Golf ball utilizing silicone materials

ABSTRACT

The present invention is directed to an improved golf ball comprising at least one interior layer and/or a core comprising a silicone material. It is preferred to also utilize a multi-layer cover in conjunction with the silicone material(s). The resulting multi-layered golf ball of the present invention provides for enhanced distance without sacrificing playability or durability when compared to known multi-layer golf balls.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims priority from U.S. provisionalpatent application serial No. 60/042,117 filed Mar. 28, 1997.

FIELD OF THE INVENTION

[0002] The present invention relates to golf balls and, moreparticularly, to improved golf balls comprising one or more interiorlayers and/or a core comprising one or more silicone materials. Theimproved golf balls provide enhanced distance and durability propertieswhile at the same time offering the “feel” is and spin characteristicsassociated with certain prior art golf balls.

BACKGROUND OF THE INVENTION

[0003] A number of two-piece (a solid resilient center or core with amolded cover) and three-piece (a liquid or solid center, elastomericwinding about the center, and a molded cover) golf balls have beenproduced by the present inventors and others. The different types ofmaterials utilized to formulate the cores, covers, etc. of these ballsdramatically alters the balls' overall characteristics. In addition,multi-layered covers containing one or more ionomer resins have alsobeen formulated in an attempt to produce a golf ball having the overalldistance, playability and durability characteristics desired.

[0004] Despite the great numbers of different materials and combinationsof materials utilized in prior art golf balls, there still remains aneed for an improved golf ball exhibiting superior properties.

[0005] The present invention is directed to new golf ball compositions,preferably utilized in conjunction with multi-layer covers, whichprovide for enhanced coefficient of restitution (i.e, enhancedresilience or carrying distance) and/or durability properties whencompared to the balls found in the prior art. As such, the playabilitycharacteristics (i.e., “feel”, “click”, “spin”, etc.) are notdiminished.

[0006] These and other objects and features of the invention will beapparent from the following summary and description of the invention,the drawings and from the claims.

SUMMARY OF THE INVENTION

[0007] The present invention provides, in one aspect, a golf ballcomprising a core, a cover layer, and at least one interior layersurrounding the core. The core and/or the interior layer include one ormore silicone materials. The silicone materials are silicone polymers,silicone fluids, silicone elastomers, and silicone resins.

[0008] In another aspect, the present invention provides a golf ballcomprising a core, an inner cover layer molded on the core, an outercover layer molded on the inner cover layer, and at least one interiorlayer between the core and the outer cover layer. The core and/or theinterior layer(s) include a silicone material.

[0009] These and other objects and features of the invention will beapparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a cross-sectional view of a preferred embodiment golfball in accordance with the present invention comprising a core and acover having an inner layer and an outer dimpled layer;

[0011]FIG. 2 is a diametrical cross-sectional view of the golf ballillustrated in FIG. 1 having a core and a cover comprising an innerlayer and an outer layer having dimples;

[0012]FIG. 3 is a partial cross-sectional view of another preferredembodiment golf ball in accordance with the present invention having aninterior layer comprising a silicone material;

[0013]FIG. 4 is a partial cross-sectional view of another preferredembodiment golf ball in accordance with the present invention having twointerior layers, at least one of which comprises a silicone-material;

[0014]FIG. 5 is a partial cross-sectional view of yet another preferredembodiment golf ball in accordance with the present invention havingthree or more interior layers, at least one of which comprises asilicone material;

[0015]FIG. 6 is a partial cross-sectional view of another preferredembodiment golf ball in accordance with the present invention having acore comprising a silicone material;

[0016]FIG. 7 is a partial cross-sectional view of another preferredembodiment golf ball in accordance with the present invention having acore comprising a silicone material and at least two interior layers;and

[0017]FIG. 8 is a partial cross-sectional view of yet another preferredembodiment golf ball in accordance with the present invention having acore comprising a silicone material and three or more interior layers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention is directed to golf balls comprising one ormore silicone interior layers and/or a silicone is core. The golf ballsof the present invention preferably utilize a multi-layer cover asdescribed herein. However, the golf balls may instead utilizeconventional cover materials such as balata or blends of balata withelastomeric or plastic materials.

[0019] The novel multi-layer golf ball covers of the present inventionpreferably include a first or inner layer or ply of a high acid (greaterthan 16 weight percent acid) ionomer or ionomer blend and second orouter layer or ply comprised of a comparatively softer, low modulusionomer, ionomer blend or other non-ionomeric thermoplastic elastomersuch as polyurethane, a polyester elastomer such as Hytrel® polyesterelastomer of E. I. DuPont de Nemours & Company, or a polyesteramide suchas the Elf Atochem S. A. Pebax® polyesteramide. Preferably, the outercover layer includes a blend of hard and soft low acid (i.e. 16 weightpercent acid or less) ionomers.

[0020] It has been found that the recently developed high acid ionomerbased inner cover layer, provides for a substantial increase inresilience (i.e., enhanced distance) over known multi-layer coveredballs. The softer outer cover layer provides for desirable “feel” andhigh spin rate while maintaining respectable resiliency. The soft outerlayer allows the cover to deform more during impact and increases thearea of contact between the club face and the cover, thereby impartingmore spin on the ball. As a result, the soft cover provides the ballwith a balata-like feel and playability characteristics with improveddistance and durability. Consequently, the overall combination of theinner and outer cover layers results in a golf ball having enhancedresilience (improved travel distance) and durability (i.e. cutresistance, etc.) characteristics while maintaining and in manyinstances, improving the ball's playability properties.

[0021] The combination of a high acid ionomer or ionomer blend innercover layer with a soft, relatively low modulus ionomer, ionomer blendor other non-ionomeric thermoplastic elastomer outer cover layerprovides for excellent overall coefficient of restitution (i.e.,excellent resilience) because of the improved resiliency produced by theinner cover layer. While some improvement in resiliency is also producedby the outer cover layer, the outer cover layer generally provides for amore desirable feel and high spin, particularly at lower swing speedswith highly lofted clubs such as half wedge shots.

[0022] Two principal properties involved in golf ball performance areresilience and hardness. Resilience is determined by the coefficient ofrestitution (C.O.R.), the constant “e” which is the ratio of therelative velocity of two elastic spheres after direct impact to thatbefore impact. As a result, the coefficient of restitution (“e”) canvary from 0 to 1, with 1 being equivalent to an elastic collision and 0being equivalent to an inelastic collision.

[0023] Resilience (C.O.R.), along with additional factors such as clubhead speed, angle of trajectory and ball configuration (i.e., dimplepattern) generally determine the distance a ball will travel when hit.Since club head speed and the angle of trajectory are factors not easilycontrollable by a manufacturer, factors of concern among manufacturersare the coefficient of restitution (C.O.R.) and the surfaceconfiguration of the ball.

[0024] The coefficient of restitution (C.O.R.) in solid core balls is afunction of the composition of the molded core and of the cover. Inballs containing a wound core (i.e., balls comprising a liquid or solidcenter, elastic windings, and a cover), the coefficient of restitutionis a function of not only the composition of the center and cover, butalso the composition and tension of the elastomeric windings. That is,both the core and the cover contribute to the coefficient ofrestitution.

[0025] In this regard, the coefficient of restitution of a golf ball isgenerally measured by propelling a ball at a given speed against a hardsurface and measuring the ball's incoming and outgoing velocityelectronically. As mentioned above, the coefficient of restitution isthe ratio of the outgoing velocity to the incoming velocity. Thecoefficient of restitution must be carefully controlled in allcommercial golf balls in order for the ball to be within thespecifications regulated by the United States Golf Association(U.S.G.A.). Along this line, the U.S.G.A. standards indicate that a“regulation” ball cannot have an initial velocity (i.e., the speed offthe club) exceeding 255 feet per second. Since the coefficient ofrestitution of a ball is related to the ball's initial velocity, it ishighly desirable to produce a ball having sufficiently high coefficientof restitution to closely approach the U.S.G.A. limit on initialvelocity, while having an ample degree of softness (i.e., hardness) toproduce enhanced playability (i.e., spin, etc.).

[0026] The hardness of the ball is the second principal propertyinvolved in the performance of a golf ball. The hardness of the ball canaffect the playability of the ball on striking and the sound or “click”produced. Hardness is determined by the deformation (i.e., compression)of the ball under various load conditions applied across the ball'sdiameter (i.e., the lower the compression value, the harder thematerial). As indicated in U.S. Pat. No. 4,674,751, softer covers permitthe accomplished golfer to impart proper spin. This is because thesofter covers deform on impact significantly more than balls having“harder” ionomeric resin covers. As a result, the better player isallowed to impart fade, draw or backspin to the ball thereby enhancingplayability. Such properties may be determined by various spin ratetests.

[0027] Another important feature of the present invention golf balls isthe use of one or more interior layers of a silicone composition. Inaddition to, or instead of, such silicone layers, the present inventiongolf balls may also comprise a core of a silicone composition. Thesesilicone materials and their incorporation into the present inventiongolf balls are described in greater detail below.

[0028]FIGS. 1 and 2 illustrate a preferred embodiment golf ball 5 inaccordance with the present invention. The golf ball 5 comprises amulti-layered cover 12 disposed about a solid core 10. The presentinvention also provides a method for making such golf balls. It will beunderstood that the referenced figures, i.e. FIGS. 1-8, are not toscale. And so, thicknesses of the various layers may be less (orgreater) than illustrated in the figures.

[0029] The multi-layered cover 12 comprises two layers: a first or innercover layer or ply 14 and a second or outer cover layer or ply 16. Theouter layer 16 defines a plurality of dimples 18. The inner layer 14 iscomprised of a high acid (i.e. greater than 16 weight percent acid)ionomer resin or high acid ionomer blend. Preferably, the inner layer iscomprised of a blend of two or more high acid (i.e. at least 16 weightpercent acid) ionomer resins neutralized to various extents by differentmetal cations. The inner cover layer may or may not include a metalstearate (e.g., zinc stearate) or other metal fatty acid salt. Theprimary purpose of the metal stearate or other metal fatty acid salt isto lower the cost of production without affecting the overallperformance of the finished golf ball.

[0030] Inner Cover Layer

[0031] The inner layer compositions include the high acid ionomers suchas those recently developed by E. I. DuPont de Nemours & Company underthe trademark “Surlyn®” and by Exxon Corporation under the trademark“Escore®” or tradename “Iotek”, or blends thereof. Examples ofcompositions which may be used as the inner layer herein are set forthin detail in U.S. Pat. No. 5,688,869, incorporated herein by reference.Of course, the inner layer high acid ionomer compositions are notlimited in any way to those compositions set forth in that '869 patent.For example, the high acid ionomer resins recently developed by Spalding& Evenflo Companies, Inc., the assignee of the present invention, anddisclosed in the '869 patent, may also be utilized to produce the innerlayer of the multi-layer cover used in the present invention.

[0032] The high acid ionomers which may be suitable for use informulating the inner layer compositions of the subject invention areionic copolymers which are the metal, i.e., sodium, zinc, magnesium,etc., salts of the reaction product of an olefin having from about 2 to8 carbon atoms and an unsaturated monocarboxylic acid having from about3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers ofethylene and either acrylic or methacrylic acid. In some circumstances,an additional comonomer such as an acrylate ester (i.e., iso- orn-butylacrylate, etc.) can also be included to produce a softerterpolymer. The carbgxylic acid groups of the copolymer are partiallyneutralized (i.e., approximately 10-75%, preferably 30-70%) by the metalions. Each of the high acid ionomer resins which may be included in theinner layer cover compositions of the invention contains greater thanabout 16% by weight of a carboxylic acid, preferably from about 17% toabout 25% by weight of a carboxylic acid, more preferably from about18.5% to about 21.5 % by weight of a carboxylic acid.

[0033] Although the inner layer cover composition preferably includes ahigh acid ionomeric resin and the scope of the patent embraces all knownhigh acid ionomeric resins falling within the parameters set forthabove, only a relatively limited number of these high acid ionomericresins have recently become commercially available.

[0034] The high acid ionomeric resins available from Exxon under thedesignation “Escor®” and or “Iotek”, are somewhat similar to the highacid ionomeric resins available under the “Surlyn®” trademark. However,since the Escor®/Iotek ionomeric resins are sodium or zinc salts ofpoly(ethylene-acrylic acid) and the “Surlyn®” resins are zinc, sodium,magnesium, etc. salts of poly(ethylene-methacrylic acid), distinctdifferences in properties exist.

[0035] Examples of the high acid methacrylic acid based ionomers foundsuitable for use in accordance with this invention include Surlyn®AD-8422 (sodium cation), Surlyn® 8162 (zinc cation), Surlyn® SEP-503-1(zinc cation), and Surlyn® SEP-503-2 (magnesium cation). According toDuPont, all of these ionomers contain from about 18.5 to about 21.5% byweight methacrylic acid.

[0036] More particularly, Surlyn® AD-8422 is currently commerciallyavailable from DuPont in a number of different grades (i.e., AD-8422-2,AD-8422-3, AD-8422-5, etc.) based upon differences in melt index.According to DuPont, Surlyn® AD-8422 offers the following generalproperties, as set forth below in Table 1, when compared to Surlyn®8920, the stiffest, hardest of all of the low acid grades (referred toas “hard” ionomers in U.S. Pat. No. 4,884,814). TABLE 1 GeneralProperties of Surlyn ® Ionomers LOW ACID (15 wt % HIGH ACID Acid) (>20wt % Acid) SURLYN ® SURLYN ® SURLYN ® 8920 8422-2 8422-3 IONOMER CationNa Na Na Melt Index 1.2 2.8 1.0 Sodium, Wt % 2.3 1.9 2.4 Base Resin MI60 60 60 MP¹, ° C. 88 86 85 FP¹, ° C. 47 48.5 45 COMPRESSION MOLDING²Tensile Break, psi 4350 4190 5330 Yield, psi 2880 3670 3590 Elongation,% 315 263 289 Flex Mod, K psi 53.2 76.4 88.3 Shore D hardness 66 67 68

[0037] In comparing Surlyn® 8920 to Surlyn® 8422-2 and Surlyn® 8422-3,it is noted that the high acid Surlyn® 8422-2 and 8422-3 ionomers have ahigher tensile yield, lower elongation, slightly higher Shore D hardnessand much higher flexural modulus. Surlyn® 8920 contains 15 weightpercent methacrylic acid and is 59% neutralized with sodium.

[0038] In addition, Surlyn® SEP-503-1 (zinc cation) and Surlyn®SEP-503-2 (magnesium cation) are high acid zinc and magnesium versionsof the Surlyn® AD 8422 high acid ionomers. As shown in Table 2, whencompared to the Surlyn® AD 8422 high acid ionomers, the Surlyn SEP-503-1and SEP-503-2 ionqmers can be defined as follows: TABLE 2 Other Surlyn ®Ionomers Surlyn ® Ionomer Ion Melt Index Neutralization % AD 8422-3 Na1.0 45 SEP 503-1 Zn 0.8 38 SEP 503-2 Mg 1.8 43

[0039] Furthermore, Surlyn® 8162 is a zinc cation ionomer resincontaining approximately 20% by weight (i.e. 18.5-21.5% weight)methacrylic acid copolymer that has been 30-70% neutralized. Surlyn®8162 is currently commercially available from DuPont.

[0040] Examples of the high acid acrylic acid based ionomers suitablefor use in the present invention also include the Escor® or Iotek highacid ethylene acrylic acid ionomers produced by Exxon. In this regard,Escor® or Iotek 959 is a sodium ion neutralized ethylene-acrylicneutralized ethylene-acrylic acid copolymer. According to Exxon, Ioteks959 and 960 contain from about 19.0 to about 21.0% by weight acrylicacid with approximately 30 to about 70 percent of the acid groupsneutralized with sodium and zinc ions, respectively. As set forth inTable 3, the physical properties of these high acid acrylic acid basedionomers are as follows: TABLE 3 General Properties of Escor ® IonomersESCOR ® ESCOR ® PROPERTY (IOTEK) 959 (IOTEK) 960 Melt Index, g/10 min2.0 1.8 Cation Sodium zinc Melting Point, ° F. 172 174 Vicat SofteningPoint, ° F. 130 131 Tensile @ Break, psi 4600 3500 Elongation @ Break, %325 430 Hardness, Shore D 66 57 Flexural Modulus, psi 66,000 27,000

[0041] Furthermore, as a result of the development by the inventors of anumber of new high acid ionomers neutralized to various extents byseveral different types of metal cations, such as by manganese, lithium,potassium, calcium and nickel cations, several new high acid ionomersand/or high acid ionomer blends besides sodium, zinc and magnesium highacid ionomers or ionomer blends are now available for golf ball coverproduction. It has been found that these new cation neutralized highacid ionomer blends produce inner cover layer compositions exhibitingenhanced hardness and resilience due to synergies which occur duringprocessing. Consequently, the metal cation neutralized high acid ionomerresins recently produced can be blended to produce substantially harderinner cover layers for multi-layered golf balls having higher C.O.R.'sthan those produced by the low acid ionomer inner cover compositionspresently commercially available.

[0042] More particularly, several new metal cation neutralized high acidionomer resins have been produced by the inventors by neutralizing, tovarious extents, high acid copolymers of an alpha-olefin and an alpha,beta-unsaturated carboxylic acid with a wide variety of different metalcation salts. This discovery is the subject matter of U.S. Pat. No.5,688,869, incorporated herein by reference. It has been found thatnumerous new metal cation neutralized high acid ionomer resins can beobtained by reacting a high acid copolymer (i.e. a copolymer containinggreater than 16% by weight acid, preferably from about 17 to about 25weight percent acid, and more preferably about 20 weight percent acid),with a metal cation salt capable of ionizing or neutralizing thecopolymer to the extent desired (i.e. from about 10% to 90%).

[0043] The base copolymer is made up of greater than 16% by weight of analpha, beta-unsaturated carboxylic acid and an alpha-olefin. Optionally,a softening comonomer can be included in the copolymer. Generally, thealpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene,and the unsaturated carboxylic acid is a carboxylic acid having fromabout 3 to 8 carbons. Examples of such acids include acrylic acid,methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid,maleic acid, fumaric acid, and itaconic acid, with acrylic acid beingpreferred.

[0044] The softening comonomer that can be optionally included in theinvention may be selected from the group consisting of vinyl esters ofaliphatic carboxylic acids wherein the acids have 2 to 10 carbon atoms,vinyl ethers wherein the alkyl groups contain 1 to 10 carbon atoms, andalkyl acrylates or methacrylates wherein the alkyl group contain 1 to 10carbon atoms. Suitable softening comonomers include vinyl acetate,methyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate, butyl methacrylate, or the like.

[0045] Consequently, examples of a number of copolymers suitable for useto produce the high acid ionomers included in the present inventioninclude, but are not limited to, high acid embodiments of anethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer,an ethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer,an ethylene/methacrylic acid/vinyl acetate copolymer, anethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymerbroadly contains greater than 16% by weight unsaturated carboxylic acid,from about 30 to about 83% by weight ethylene and from 0 to about 40% byweight of a softening comonomer. Preferably, the copolymer containsabout 20% by weight unsaturated carboxylic acid and about 80% by weightethylene. Most preferably, the copolymer contains about 20% acrylic acidwith the remainder being ethylene.

[0046] Along these lines, examples of the preferred high acid basecopolymers which fulfill the criteria set forth above, are a series ofethylene-acrylic copolymers which are commercially available from TheDow Chemical Company, Midland, Mich., under the “Primacor” designation.These high acid base copolymers exhibit the typical properties set forthbelow in Table 4. TABLE 4 Typical Properties of PrimacorEthylene-Acrylic Acid Copolymers MELT TENSILE FLEXURAL VICAT PERCENTDENSITY, INDEX, YD. ST MODULUS SOFT PT SHORE D GRADE ACID glcc g/10 min(psi) (psi) (° C.) HARDNESS ASTM D-792 D-1238 D-638 D-790 D-1525 D-22405980 20.0 0.958  300.0 — 4800 43 50 5990 20.0 0.955 1300.0 650 2600 4042 5981 20.0 0.960  300.0 900 3200 46 48 5983 20.0 0.958  500.0 850 310044 45 5991 20.0 0.953 2600.0 635 2600 38 40

[0047] Due to the high molecular weight of the Primacor 5981 grade ofthe ethylene-acrylic acid copolymer, this copolymer is the morepreferred grade utilized in the invention.

[0048] The metal cation salts utilized in the invention are those saltswhich provide the metal cations capable of neutralizing, to variousextents, the carboxylic acid groups of the high acid copolymer. Theseinclude acetate, oxide or hydroxide salts of lithium, calcium, zinc,sodium, potassium, nickel, magnesium, and manganese.

[0049] Examples of such lithium ion sources are lithium hydroxidemonohydrate, lithium hydroxide, lithium oxide and lithium acetate.Sources for the calcium ion include calcium hydroxide, calcium acetateand calcium oxide. Suitable zinc ion sources are zinc acetate dihydrateand zinc acetate, a blend of zinc oxide and acetic acid. Examples ofsodium ion sources are sodium hydroxide and sodium acetate. Sources forthe potassium ion include potassium hydroxide and potassium acetate.Suitable nickel ion sources are nickel acetate, nickel oxide and nickelhydroxide. Sources of magnesium include magnesium oxide, magnesiumhydroxide, magnesium acetate. Sources of manganese include manganeseacetate and manganese oxide.

[0050] The new metal cation neutralized high acid ionomer resins areproduced by reacting the high acid base copolymer with various amountsof the metal cation salts above the crystalline melting point of thecopolymer, such as at a temperature from about 200° F. to about 500° F.,preferably from about 250° F. to about 350° F. under high shearconditions at a pressure of from about 10 psi to 10,000 psi. Other wellknown blending techniques may also be used. The amount of metal cationsalt utilized to produce the new metal cation neutralized high acidbased ionomer resins is the quantity which provides a sufficient amountof the metal cations to neutralize the desired percentage of thecarboxylic acid groups in the high acid copolymer. The extent ofneutralization is generally from about 10% to about 90%.

[0051] As indicated below in Table 5 and more specifically in theExamples in U.S. Pat. No. 5,688,869 a number of new types of metalcation neutralized high acid ionomers can be obtained from the aboveindicated process. These include new high acid ionomer resinsneutralized to various extents with manganese, lithium, potassium,calcium and nickel cations. In addition, when a high acidethylene/acrylic acid copolymer is utilized as the base copolymercomponent of the invention and this component is subsequentlyneutralized to various extents with the metal cation salts producingacrylic acid based high acid ionomer resins neutralized with cationssuch as sodium, potassium, lithium, zinc, magnesium, manganese, calciumand nickel, several new cation neutralized acrylic acid based high acidionomer resins are produced. TABLE 5 Formulation Wt-% Wt-% Melt Shore DNo. Cation Salt Neutralization Index C.O.R. Hardness 1(NaOH) 6.98 67.50.9 .804 71 2(NaOH) 5.66 54.0 2.4 .808 73 3(NaOH) 3.84 35.9 12.2 .812 694(NaOH) 2.91 27.0 17.5 .812 (brittle) 5(MnAc) 19.6 71.7 7.5 .809 736(MnAc) 23.1 88.3 3.5 .814 77 7(MnAc) 15.3 53.0 7.5 .810 72 8(MnAc) 26.5106 0.7 .813 (brittle) 9(LiOH) 4.54 71.3 0.6 .810 74 10(LiOH) 3.38 52.54.2 .818 72 11(LiOH) 2.34 35.9 18.6 .815 72 12(KOH) 5.30 36.0 19.3 Broke70 13(KOH) 8.26 57.9 7.18 .804 70 14(KOH) 10.7 77.0 4.3 .801 67 15(ZnAc)17.9 71.5 0.2 .806 71 16(ZnAc) 13.9 53.0 0.9 .797 69 17(ZnAc) 9.91 36.13.4 .793 67 18(MgAc) 17.4 70.7 2.8 .814 74 19(MgAc) 20.6 87.1 1.5 .81576 20(MgAc) 13.8 53.8 4.1 .814 74 21(CaAc) 13.2 69.2 1.1 .813 7422(CaAc) 7.12 34.9 10.1 .808 70 23(MgO) 2.91 53.5 2.5 .813 24(MgO) 3.8571.5 2.8 .808 25(MgO) 4.76 89.3 1.1 .809 26(MgO) 1.96 35.7 7.5 .81527(NiAc) 13.04 61.1 0.2 .802 71 28(NiAc) 10.71 48.9 0.5 .799 72 29(NiAc)8.26 36.7 1.8 .796 69 30(NiAc) 5.66 24.4 7.5 .786 64

[0052] When compared to low acid versions of similar cation neutralizedionomer resins, the new metal cation neutralized high acid ionomerresins exhibit enhanced hardness, modulus and resiliencecharacteristics. These are properties that are particularly desirable ina number of thermoplastic fields, including the field of golf ballmanufacturing.

[0053] When utilized in the construction of the inner layer of amulti-layered golf ball, it has been found that the new acrylic acidbased high acid ionomers extend the range of hardness beyond thatpreviously obtainable while maintaining the beneficial properties (i.e.durability, click, feel, etc.) of the softer low acid ionomer coveredballs, such as balls produced utilizing the low acid ionomers disclosedin U.S. Pat. Nos. 4,884,814 and 4,911,451.

[0054] Moreover, as a result of the development of a number of newacrylic acid based high acid ionomer resins neutralized to variousextents by several different types of metal cations, such as manganese,lithium, potassium, calcium and nickel cations, several new ionomers orionomer blends are now available for production of an inner cover layerof a multi-layered golf ball. By using these high acid ionomer resins,harder, stiffer inner cover layers having higher C.O.R.s, and thuslonger distance, can be obtained.

[0055] More preferably, it has been found that when two or more of theabove-indicated high acid ionomers, particularly blends of sodium andzinc high acid ionomers, are processed to produce the covers ofmulti-layered golf balls, (i.e., the inner cover layer herein) theresulting golf balls will travel further than previously knownmulti-layered golf balls produced with low acid ionomer resin covers dueto the balls' enhanced coefficient of restitution values.

[0056] For example, the multi-layer golf ball taught in U.S. Pat. No.4,650,193 does not incorporate a high acid ionomeric resin in the innercover layer. The coefficient of restitution of the golf ball having aninner layer taught by the '193 patent (i.e., inner layer composition “D”in the Examples) is substantially lower than the coefficient ofrestitution of the remaining compositions. In addition, themulti-layered ball disclosed in the '193 patent suffers substantially indurability in comparison with the present invention.

[0057] Outer Cover Layer

[0058] With respect to the outer layer 16 of the preferred multi-layeredcover, the outer cover layer is comparatively softer than the high acidionomer based inner layer. The softness provides for the feel andplayability characteristics typically associated with balata orbalata-blend balls. The outer layer or ply is comprised of a relativelysoft, low modulus (about 1,000 psi to about 10,000 psi) and low acid(less than 16 weight percent acid) ionomer, ionomer blend or anon-ionomeric thermoplastic elastomer such as, but not limited to, apolyurethane, a polyester elastomer such as that marketed by DuPontunder the trademark Hytrel®, or a polyester amide such as that marketedby Elf Atochem S.A. under the trademark Pebax®. The outer layer isfairly thin (i.e. from about 0.010 to about 0.050 in thickness, moredesirably 0.03 inches in thickness for a 1.680 inch ball), but thickenough to achieve desired playability characteristics while minimizingexpense.

[0059] Preferably, the outer layer includes a blend of hard and soft(low acid) ionomer resins such as those described in U.S. Pat. Nos.4,884,814 and 5,120,791, both incorporated herein by reference.Specifically, a desirable material for use in molding the outer layercomprises a blend of a high modulus (hard) ionomer with a low modulus(soft) ionomer to form a base ionomer mixture. A high modulus ionomerherein is one which measures from about 15,000 to about 70,000. psi asmeasured in accordance with ASTM method D-790. The hardness may bedefined as at least 50 on the Shore D scale as measured in accordancewith ASTM method D-2240.

[0060] A low modulus ionomer suitable for use in the outer layer blendhas a flexural modulus measuring from-about 1,000 to about 10,000 psi,with a hardness of about 20 to about 40 on the Shore D scale.

[0061] The hard ionomer resins utilized to produce the outer cover layercomposition hard/soft blends include ionic copolymers which are thesodium, zinc, magnesium or lithium salts of the reaction product of anolefin having from 2 to 8 carbon atoms and an unsaturated monocarboxylicacid having from 3 to 8 carbon atoms. The carboxylic acid groups of thecopolymer may be totally or partially (i.e. approximately 15-75 percent)neutralized.

[0062] The hard ionomeric resins are likely copolymers of ethylene andeither acrylic and/or methacrylic acid, with copolymers of ethylene andacrylic acid being the most preferred. Two or more types of hardionomeric resins may be blended into the outer cover layer compositionsin order to produce the desired properties of the resulting golf balls.

[0063] As discussed earlier herein, the hard ionomeric resins introducedunder the designation Escor® and sold under the designation “Iotek” aresomewhat similar to the hard ionomeric resins sold under the Surlyn®trademark. However, since the “Iotek” ionomeric resins are sodium orzinc salts of poly(ethylene-acrylic acid) and the Surlyn® resins arezinc or sodium salts of poly(ethylene-methacrylic acid) some distinctdifferences in properties exist. As more specifically indicated in thedata set forth below, the hard “Iotek” resins (i.e., the acrylic acidbased hard ionomer resins) are the more preferred hard resins for use informulating the outer layer blends for use in the present invention. Inaddition, various blends of “Iotek” and Surlyn® hard ionomeric resins,as well as other available ionomeric resins, may be utilized in thepresent invention in a similar manner.

[0064] Examples of commercially available hard ionomeric resins whichmay be used in the present invention in formulating the outer coverblends include the hard sodium ionic copolymer sold under the trademarkSurlyn®8940 and the hard zinc ionic copolymer sold under the trademarkSurlyn®9910. Surlyn®8940 is a copolymer of ethylene with methacrylicacid and about 15 weight percent acid which is about 29 percentneutralized with sodium ions. This resin has an average melt flow indexof about 2.8. Surlyn®9910 is a copolymer of ethylene and methacrylicacid with about 15 weight percent acid which is about 58 percentneutralized with zinc ions. The average melt flow index of Surlyn®9910is about 0.7. The typical properties of Surlyn®9910 and 8940 are setforth below in Table 6: TABLE 6 Typical Properties of CommerciallyAvailable Hard Surlyn ® Resins Suitable for Use in the Outer LayerBlends of the Present Invention ASTM D 8940 9910 8920 8528 9970 9730Cation Type Sodium Zinc Sodium Sodium Zinc Zinc Melt flow index, D-12382.8 0.7 0.9 1.3 14.0 1.6 gms/10 min. Specific Gravity, D-792 0.95 0.970.95 0.94 0.95 0.95 g/cm³ Hardness, Shore D D-2240 66 64 66 60 62 63Tensile Strength, D-638 (4.8)  (3.6)  (5.4)  (4.2)  (3.2)  (4.1) (kpsi), MPa 33.1 24.8 37.2 29.0 22.0 28.0 Elongation, % D-638 470 290350 450 460 460 Flexural Modulus, D-790 (51)   (48)   (55)   (32)  (28)   (30)   (kpsi) MPa 350 330 380 220 190 210 Tensile Impact (23° C.)D-1822S 1020 1020 865 1160 760 1240 KJ/m₂ (ft.-lbs./in²) (485)  (485) (410)  (550)  (360)  (590)  Vicat Temperature, ° C. D-1525 63 62 58 7361 73

[0065] Examples of the more pertinent acrylic acid based hard ionomerresin suitable for use in the present outer cover composition sold underthe “Iotek” tradename by the Exxon Corporation include Iotek 4000, Iotek4010, Iotek 8000, Iotek 8020 and Iotek 8030. The typical properties ofthese and other Iotek hard ionomers suited for use in formulating theouter layer cover composition are set forth below in Table 7: TABLE 7Typical Properties of Iotek Ionomers ASTM Method Units 4000 4010 80008020 8030 Resin Properties Cation type zinc zinc sodium sodium sodiumMelt index D-1238 g/10 min. 2.5 1.5 0.8 1.6 2.8 Density D-1505 kg/m³ 963963 954 960 960 Melting Point D-3417 ° C. 90 90 90 87.5 87.5Crystallization Point D-3417 ° C. 62 64 56 53 55 Vicat Softening PointD-1525 ° C. 62 63 61 64 67 % Weight Acrylic Acid 16 11 % of Acid Groups30 40 cation neutralized Plaque Properties (3 mm thick, compressionmolded) Tensile at break D-638 MPa 24 26 36 31.5 28 Yield point D-638MPa none none 21 21 23 Elongation at break D-638 % 395 420 350 410 3951% Secant modulus D-638 MPa 160 160 300 350 390 Shore Hardness D D-2240— 55 55 61 58 59 Film Properties (50 micron film 2.2:1 Blow-up ratio)Tensile at Break MD D-882 MPa 41 39 42 52 47.4 TD D-882 MPa 37 38 38 3840.5 Yield point MD D-882 MPa 15 17 17 23 21.6 TD D-882 MPa 14 15 15 2120.7 Elongation at Break MD D-882 % 310 270 260 295 305 TD D-882 % 360340 280 340 345 1% Secant modulus MD D-882 MPa 210 215 390 380 380 TDD-882 MPa 200 225 380 350 345 Dart Drop Impact D-1709 g/micron 12.4 12.520.3 ASTM Method Units 7010 7020 7030 Resin Properties Cation type zinczinc zinc Melt Index D-1238 g/10 min. 0.8 1.5 2.5 Density D-1505 kg/m³960 960 960 Melting Point D-3417 ° C. 90 90 90 Crystallization D-3417 °C. — — — Point Vicat Softening D-1525 ° C. 60 63 62.5 Point % WeightAcrylic Acid — — — % of Acid Groups — — — Cation Neutralized (3 mmthick, compression molded) Tensile at break D-638 MPa 38 38 38 YieldPoint D-638 MPa none none none Elongation at break D-638 % 500 420 3951% Secant modulus D-638 MPa — — — Sh re Hardness D D-2240 — 57 55 55

[0066] Comparatively, soft ionomers are used in formulating thehard/soft blends of the outer cover composition. These ionomers includeacrylic acid based soft ionomers. They are generally characterized ascomprising sodium or zinc salts of a terpolymer of an olefin having fromabout 2 to 8 carbon atoms, acrylic acid, and an unsaturated monomer ofthe acrylate ester class having from 1 to 21 carbon atoms.. The softionomer is preferably a zinc based ionomer made from an acrylic acidbase polymer in an unsaturated monomer of the acrylate ester class. Thesoft (low modulus) ionomers have a hardness from about 20 to about 40 asmeasured on the Shore D scale and a flexural modulus from about 1,000 toabout 10,000, as measured in accordance with ASTM method D-790.

[0067] Certain ethylene-acrylic acid based soft ionomer resins developedby the Exxon Corporation under the designation “Iotek 7520” (referred toexperimentally by differences in neutralization and melt indexes as LDX195, LDX 196, LDX 218 and LDX 219) may be combined with known hardionomers such as those indicated above to produce the outer cover. Thecombination produces higher C.O.R.s at equal or softer hardness, highermelt flow (which corresponds to improved, more efficient molding, i.e.,fewer rejects) as well as significant cost savings versus the outerlayer of multi-layer balls produced by other known hard-soft ionomerblends as a result of the lower overall raw materials costs and improvedyields.

[0068] While the exact chemical composition of the resins to be sold byExxon under the designation Iotek 7520 is considered by Exxon to beconfidential and proprietary information, Exxon's experimental productdata sheet lists the following physical properties of the ethyleneacrylic acid zinc ionomer developed by Exxon: TABLE 8 Property ASTMMethod Units Typical Value Physical Properties of Iotek 7520 Melt IndexD-1238 g/10 min. 2 Density D-1505 kg/m³ 0.962 Cation Zinc Melting PointD-3417 ° C. 66 Crystallization Point D-3417 ° C. 49 Vicat SofteningPoint D-1525 ° C. 42 Plaque Properties (2 mm thick Compression MoldedPlaques) Tensile at Break D-638 MPa 10 Yield Point D-638 MPa NoneElongation at Break D-638 % 760 1% Secant Modulus D-638 MPa 22 Shore DHardness D-2240 32 Flexural Modulus D-790 MPa 26 Zwick Rebound ISO 4862% 52 De Mattia Flex D-430 Cycles >5000 Resistance

[0069] In addition, test data collected by the inventors indicates thatIotek 7520 resins have Shore D hardnesses of about 32 to 36 (per ASTMD-2240), melt flow indexes of 3±0.5 g/10 min (at 190° C. per ASTMD-1288), and a flexural modulus of about 2500-3500 psi (per ASTM D-790).Furthermore, testing by an independent testing laboratory by pyrolysismass spectrometry indicates that Iotek 7520 resins are generally zincsalts of a terpolymer of ethylene, acrylic acid, and methyl acrylate.

[0070] Furthermore, the inventors have found that a newly developedgrade of an acrylic acid based soft ionomer available from the ExxonCorporation under the designation Iotek 7510, is also effective, whencombined with the hard ionomers indicated above in producing golf ballcovers exhibiting higher C.O.R. values at equal or softer hardness thanthose produced by known hard-soft ionomer blends. In this regard, Iotek7510 has the advantages (i.e. improved flow, higher C.O.R. values atequal hardness, increased clarity, etc.) produced by the Iotek 7520resin when compared to the methacrylic acid base soft ionomers known inthe art (such as the Surlyn 8625 and the Surlyn 8629 combinationsdisclosed in U.S. Pat. No. 4,884,814).

[0071] In addition, Iotek 7510, when compared to Iotek 7520, producesslightly higher C.O.R. values at equal softness/hardness due to theIotek 7510's higher hardness and neutralization. Similarly, Iotek 7510produces better release properties (from the mold cavities) due to itsslightly higher stiffness and lower flow rate than Iotek 7520. This isimportant in production where the soft covered balls tend to have loweryields caused by sticking in the molds and subsequent punched pin marksfrom the knockouts.

[0072] According to Exxon, Iotek 7510 is of similar chemical compositionas Iotek 7520 (i.e. a zinc salt of a terpoloymer of ethylene, acrylicacid, and methyl acrylate) but is more highly neutralized. Based uponFTIR analysis, Iotek 7520 is estimated to be about 30-40 wt.-%neutralized and Iotek 7510 is estimated to be about 40-60 wt.-%neutralized. The typical properties of Iotek 7510 in comparison of thoseof Iotek 7520 are set forth below in Table 9: TABLE 9 PhysicalProperties of Iotek 7510 in Comparison to Iotek 7520 IOTEK 7520 IOTEK7510 MI, g/10 min 2.0 0.8 Density, g/cc 0.96 0.97 Melting Point, ° F.151 149 Vicat Softening Point, ° F. 108 109 Flex Modulus, psi 3800 5300Tensile Strength, psi 1450 1750 Elongation, % 760 690 Hardness, Shore D32 35

[0073] It has been determined that when hard/soft ionomer blends areused for the outer cover layer, good results are achieved when therelative combination is in a range of about 90 to about 10 percent hardionomer and about 10 to about 90 percent soft ionomer. The results areimproved by adjusting the range to about 75 to 25 percent hard ionomerand 25 to 75 percent soft ionomer. Even better results are noted atrelative ranges of about 60 to 90 percent hard ionomer resin and about40 to 60 percent soft ionomer resin. Specific formulations which may beused in the cover composition are included in the examples set forth inU.S. Pat. Nos. 5,120,791 and 4,884,814. The present invention is in noway limited to those examples.

[0074] Moreover, in alternative embodiments, the outer cover layerformulation may also comprise a soft, low modulus non-ionomericthermoplastic elastomer including a polyester polyurethane such as B. F.Goodrich Company's Estane® polyester polyurethane X-4517. According toB. F. Goodrich, Estane® X-4517 has the following properties as set forthbelow in Table 10: TABLE 10 Properties of Estane ® X-4517 Tensile 1430100%  815 200% 1024 300% 1193 Elongation  641 Youngs Modulus 1826Hardness A/D 88/39 Bayshore Rebound  59 Solubility in Water InsolubleMelt processing temperature >350° F. (>177° C.) Specific Gravity (H₂O= 1) 1.1-1.3

[0075] Other soft, relatively low modulus non-ionomeric thermoplasticelastomers may also be utilized to produce the outer cover layer as longas the non-ionomeric thermoplastic elastomers produce the playabilityand durability characteristics desired without adversely effecting theenhanced travel distance characteristic produced by the high acidionomer resin composition. These include, but are not limited tothermoplastic polyurethanes such as: Texin thermoplastic polyurethanesfrom Mobay Chemical Co. and the Pellethane thermoplastic polyurethanesfrom Dow Chemical Co.; Ionomer/rubber blends such as those in SpaldingU.S. Pat. Nos. 4,986,545; 5,098,105 and 5,187,013; and, Hytrel polyesterelastomers from DuPont and pebax polyesteramides from Elf Atochem S.A.

[0076] Silicone Interior Layers and/or Core

[0077] The present invention golf ball as previously noted, comprisesone or more interior layers comprising one or more siliconecompositions. The present invention golf ball may also, in addition tothese silicone interior layers, comprise a core or core layer(s)comprising one or more silicone materials. The terms “siliconecomposition” and “silicone material” as used herein are interchangeablefor purposes of this patent and comprise silicone polymers, siliconefluids, silicone elastomers, and silicone resins, each of which aredescribed in detail below. It will be understood that these varioussilicone materials are distinguishable from silica, as is used as afiller agent, as described in U.S. Pat. Nos. 5,387,637; 3,756,607; and2,764,572, all of which are herein incorporated by reference.

[0078] The term silicone as referred to herein denotes a syntheticpolymer (R_(n)SiO(_(4−n/2))_(m), where n=1-3 and m≧2. A siliconecontains a repeating silicon-oxygen backbone and has organic groups Rattached to a significant proportion of the silicon atoms bysilicon-carbon bonds. In commercially available silicones, most R groupsare methyl, longer alkyl, fluoroalkyl, phenyl, vinyl, and a few othergroups are substituted for specific purposes. Some of the R groups canalso be hydrogen, chlorine, alkoxy, acyloxy, or alkylamino, etc. Thesepolymers can be combined with fillers, additives, and solvents to resultin products generally termed as silicones.

[0079] Silicones have an unusual array of properties. Chief among theseare thermal and oxidative stability and physical properties that areminimally affected by temperature. Other important characteristicsinclude a high degree of chemical inertness, and resistance toweathering. These features are such that silicone materials are wellsuited for incorporation into golf balls in accordance with the presentinvention. The molecular structure of suitable silicones can varyconsiderably to include linear, branched, and cross-linked structures.

[0080] Like carbon, silicon has the capability of forming covalentcompounds. Silicon hyrides (silanes) up to Si₆H₁₄ are known. The Si—Sichain becomes thermally unstable at about this length, however, so thatpolymeric silanes are unknown. The siloxane link:

[0081] is more stable, and is the one predominantly found in commercialsilicone polymers. Unlike carbon, silicon does not form double or triplebonds. Thus silicone polymers are usually formed only bycondensation-type reactions.

[0082] Silicone polymers are made from organosilicon intermediatesprepared in various ways from elemental silicon, which is typicallyproduced by reducing quartz in an electric furnace.

[0083] The intermediate “monomers” of silicone polymers are compounds ofthe type S_(i)R_(n)X_(4−n) where R is an alkyl or aryl group and X is agroup which can be hydrolyzed to —SiOH, such as chlorine or alkoxy. Theintermediates are generally made by a direct synthesis in which the Rand X groups are attached simultaneously to the silicon by ahigh-temperature reaction of a halide with silicon in the presence of ametal catalyst. The chief reaction is, for example,

2CH₅Cl+Si→Si(CH₃)₂Cl₂

[0084] but a number of side reactions may occur.

[0085] Silicone polymers are typically produced by intermolecularcondensation of silanols, which are formed from the-halide or alkoxyintermediates by hydrolysis:

[0086] The desired siloxane structure is obtained by using silanols ofdifferent functionality, the alkyl R groups in the intermediate beingunreactive.

[0087] The three commercially important classes of silicone polymers foruse in the preferred embodiment golf balls include siliconehomopolymers, silicone random copolymers, and silicone-organic (block)copolymers. Polydimethylsiloxanes (PDMS) constitute by far the largestvolume of homopolymers commercially produced:

[0088] PDMS is usually the principal component of the random copolymersand the principal siloxane component of most silicone-organiccopolymers.

[0089] The most common silicones are the trimethylsiloxy-terminatedpolydimethylsiloxanes. These polymers, as well as variations withsilanol, vinyl, or hydride end groups, form the building blocks of manysilicone fluid-based products and of most cured silicone elastomers. Theproperties of polydimethylsiloxanes are typically modified bysubstitution of methyl groups on the silicon atom by hydrogen, alkyl,phenyl, or organofunctional groups.

[0090] Silicone fluids are low polymers typically produced by thehydrolysis reaction mentioned above, in which a predetermined mixture ofchlorosilanes is fed into water with agitation. In many cases, thecyclic tetramer predominates in the resulting mixture. Many siliconefluids are manufactured commercially, including dimethyl, methylalkyl,and dimethyl-diphenyl copolymers and silicone-polyether copolymers.These compounds are typically used as cooling and dielectric fluids, inpolishes and waxes, as release and antifoam agents, and for paper andtextile treatment. In view of their relatively low viscosity and fluidnature, these compounds are less preferred for use as the siliconematerials in the present invention as compared to silicone polymers, andas described below, silicone elastomers and silicone resins. However, itis contemplated that silicone fluids may be utilized in the presentinvention golf balls.

[0091] Silicone elastomers are high-molecular-weight linear polymers,usually polydimethysiloxanes. Cross-linking silicone polymers ofappropriate molecular weight provides elastomeric properties. Fillersincrease strength through reinforcement, and extending fillers andadditives, eg. antioxidants, adhesion promoters, and pigments, can beutilized to provide specific properties.

[0092] Many curing (cross-linking) systems have been developedcommercially for silicone elastomers. Different commercially availablesilicone elastomers are conveniently distinguished by their cure systemchemistries and can be categorized by the temperature conditions neededfor proper cure. Most compositions are based on polydimethylsiloxanes:

[0093] R is determined by the cure system chemistry. It can be hydrogen,an organic radical, or a silyl radical. The silyl radicals can containsingle or multiple reactive groups like vinyl or alkoxy. Small amountsof reactive functionality are sometimes present in the chain in(copolymerized) units such as (CH₂CH) (CH₃)SiO. The value of x variesmainly with the type of product. For room-temperature-vulcanizing RTVproducts, x is in the 200-1,500 range; for heat-cured products, x isapproximately 3,000-11,000.

[0094] Silicone elastomers can be cured in several ways:

[0095] a. By free-radical crosslinking with, for example, benzoylperoxide, through the formation of ethylenic bridges between chains;

[0096] b. By crosslinking of vinyl or allyl groups attached to siliconthrough reaction with silylhydride groups:

[0097] c. By crosslinking linear or slightly branched siloxane chainshaving reactive end groups such as silanols. In contrast to the abovereactions, this yields Si—O—Si crosslinks.

[0098] The latter mechanism forms the basis of the curing ofroom-temperature vulcanizing (RTV) silicone elastomers.

[0099] These are available as two-part mixtures in which all threeessential ingredients for the cure (silanol-terminated polymer,cross-linking agent such as ethyl silicate, and catalyst such as a tinsoap) are combined at the time the two components are mixed, and asone-part materials using a hydrolyzable polyfunctional silane orsiloxane as crosslinker, activated by atmospheric moisture.

[0100] Silicone elastomers are preferably reinforced by a finely dividedmaterial such as silica to more readily achieve properties for thesilicone material as utilized in the interior layer(s) or core.Specifically, the reinforcing fillers for silicone elastomers may befinely divided silicas made by fume or wet processes. The fume processprovides the highest degree of reinforcement. Accordingly, the particlesize is small. The particle diameter should be about the length of afully extended polymer chain, i.e., about 1 μm, for semireinforcementand about 0.01-0.05 μm for strong reinforcement. Fine particle size doesnot necessarily provide good reinforcement because finely dividedfillers tend to agglomerate and are hard to disperse. This tendency canbe countered by treating the filler to give it an organic or a siliconecoating before mixing it with polymer. Hexamethyldisilazane,[(CH₃)₃Si]₂NH, is sometimes used as a coupling agent. Treating thesilica particles with hot vapors of low molecular weight cyclicsiloxanes reduces agglomeration and prevents premature crepe hardening.

[0101] Nonreinforcing fillers, such as iron oxide or titanium dioxide,may be utilized to stabilize or color the resulting silicone material orto decrease the cost per unit volume.

[0102] Thus fillers of many different chemical compositions with a broadrange of particle sizes and physical properties are suitable for usewith silicone elastomers when utilized in the present invention golfballs. The particular filler(s) selected primarily-depend upon thedesired end use properties of the silicone material in the golf balls.The mechanism of reinforcement has not been unequivocally determined andmay indeed vary from one filler or polymer type to another. However,particle size is of prime importance for the strength of the elastomercompound after cure. Effective reinforcement is generally provided bysilica particles having a specific gravity of about 2 and a range ofabout 20-400 m²/g specific surface area.

[0103] Nonreinforcing fillers may also be used merely as extenders. Theparticle size of such fillers ranges from submicro-meter to about 10 μm.These fillers may not improve physical properties, but can beincorporated in significant amounts without adversely affecting strengthof the resulting silicone material. Manufacture of these extenders doesnot require the specialized technology necessary for extremely fineparticle fillers, but the selected extenders must meet rigorousrequirements of thermal stability, low volatile content, and chemicalpurity.

[0104] Silicone elastomers differ in several important ways from mostorganic elastomers. The most striking difference is the degree to whichthe strength of the final compound depends on the reinforcementconferred by the incorporation of fillers. Typical unfilled siliconegums, when cross-linked, are weak and soft, with tensile strengths onthe order of 0.34 MPa (50 psi). Compounding with suitably reinforcingfillers may increase the tensile strength as much as 50-fold. Theselection of the filler is therefore extremely important forapplications where strength is required. These differences inpolymer-filler interactions and physical property requirements makefillers suitable for silicone elastomers different from those used fornatural and synthetic rubber compounding.

[0105] The preferred filler types for silicone compounds used in thepresent invention golf balls include finely divided silicas prepared byvapor-phase hydrolysis or oxidation of chlorosilanes, dehydrated silicagels, precipitated silicas, diatomaceous silicas, and finely ground highassay natural silicas; fumed titania, alumina, and zirconia.Pigment-grade oxides especially ferric oxides, are extensively used asfillers for high temperature compounds in oxidizing environments. Theiron oxide stabilizes the polymer against atmospheric oxidation andpreserves the elastomeric characteristics, especially resilience anddeformability, after exposure to temperatures above 300° C. Carbonblacks have had limited application because of their high content ofadsorbed volatiles, which can lead to void formation during cure. Othertypes of fillers include calcium carbonate, clays, siicates, andaluminates. Fibrous fillers improve tear resistance at the expense ofelongation, and hollow glass or. plastic microspheres reduce thespecific gravity. Fillers and their effects on heat-cured rubberproperties are shown in Table 11. TABLE 11 Fillers Suitable for SiliconePolymers Reinforcement produced in Particle Size silicone gums MeanSurface Tensile Diameter, Area, Strength, Filler μm m²/q MPa Elongation,% Reinforcing fumed silica   0.03  silica 4.1-6.9 200-350 acetyleneblack 0.015-0.02  aerogel  4.1-12.4 200-600 Semireinforcing andnonreinforcing   0.045 110-150 4.1-6.2 200-350 flux-calcineddiatomaceous silica 175-200 calcined diatomaceous silica   1.5  78-852.7-5.5  75-200 calcined kaolin 1-5 2.7-5.5  75-200 precipitated calciumcarbonate 1-5 <5 2.7-5.5  75-200 ground silica 0.03-0.05 <5 2.7-4.1100-300 ground silica  5-10 <5 0.7-2.8 200-300 ground silica  1-10 320.7-2.8 200-300 zinc oxide   5    0.7-2.8 200-300 iron oxide   0.3 1.4-3.5 100-300 zirconium silicate <1    1.4-3.5 100-300 titaniumdioxide 3.0 2.8-4.1 100-300   0.3  1.4-3.5 300-400

[0106] Some silica or other oxide-filled silicone elastomers tend to“structure,” i.e., to form an elastic mass before cure, impeding normalprocessing operations such as molding and extrusion. Intensive workingof the compound with a rubber mill or other mixer may be necessary torestore plasticity. To minimize this tendency, plasticizers and processaids may be incorporated into the compounds. The most commonly usedadditives are monomeric or oligomeric organosilicon compounds. Highsurface silica filler is treated with a silicon derivative to minimizethe buildup of structure. The structuring tendency is associated withhydrogen bonding between the siloxane polymers and silanol groups on thefiller surface. The extent of hydrogen bonding is a function of theconcentration of surface silanol and varies with the type and method ofpreparation of the filler. Surface silanol concentration can be relatedto the total surface area as determined by absorption methods.Sufficient treating agent can be added to react completely with or behydrogen bonded to the silanol groups present and yield a nonstructuringrubber compound. In an early method, the filler is treated withchlorosilanes or other reactive silanes, and the HCl or other reactionproducts are removed by purging the filler mass with an inert gas.Cyclic siloxane oligomers may be used to treat filler for siliconeelastomers.

[0107] The extremely high surface silicas used as fillers present thesame storage and handling problems as conventional fluffy carbon blacks.Typical bulk densities for fumed silicas typically range from about 32to about 80 kg/m³. They can be increased to 160-240 kg/m³ by mechanicalcompaction and deaeration.

[0108] Oligomers of polydimethylsiloxane can be polymerized in thepresence of fillers. Uncatalyzed base compounds for both RTV andheat-curing elastomers can be made in this way. However, optimalproperties still depend on conventional compounding.

[0109] Related to silicone elastomers, room temperature vulcanizing(RTV) silicone elastomers are often available as uncured rubbers withliquid or paste like consistencies. They are based on polymers ofintermediate molecular weights and viscosities, e.g., 100-1,000,000mm²/s at 25° C. Curing is based on chemical reactions that increasemolecular weights and provide cross-linking. Catalysts may be utilizedto ensure cure control. The RTV silicone rubbers are typically availablein two modifications. The cure reactions of one-component products aretriggered by exposure to atmospheric moisture. Those of two-componentproducts are triggered by mixing the two components, one of whichconsists of or contains the catalyst.

[0110] Commercially available one-component RTV rubbers are typicallymade by mixing polymers, fillers, additives, curing agents, andcatalysts. The mixture is packaged to protect it from moisture, whichmay trigger cure. The time required for cure depends on the curingsystem, temperature, humidity, and thickness of the silicone layer orcore component. Under typical ambient conditions the surface can be tackfree in about 30 minutes, while a 0.3-cm thick layer cures in less thanone day. As cure progresses, strength develops slowly for about threeweeks.

[0111] The original viscosity of these RTV materials depends principallyon that of the polymer components and the filler loading. Filler andoriginal polymer properties and cross-link density affect the ultimatestrength of the fully cured elastomer. Most commercially availableproducts are based on polydimethylsiloxanes. Polymers with substituentsother than methyl modify and improve certain properties; e.g.,trifluoropropyl groups improve solvent resistance. Some products arecompounded with fillers and additives to be pourable, and others to bethixotropic. Silica-filled polydimethylsiloxane systems, lackingpigments and other additives, cure to form translucent rubbers. Sincethe specific gravity of silicas, generally about 2.2, exceeds that ofsiloxanes, generally about 1.0, the specific gravity of the RTV rubbersdepends on the filler loading. Physical properties of similar curedacetoxy RTV formulations are shown in Table 12. TABLE 12 PhysicalProperties of RTV Rubbers Durometer Hardness, Specific Gravity¹ Shore ATensile Strength, MPa Elongation, % 1.18 45 2.4 180 1.30 50 3.1 140 1.3350 3.4 200 1.37 55 3.8 120 1.45 60 4.5 110 1.45 60 5.2 160 1.48 65 4.8110

[0112] Formulations with different curing systems, polymer molecularweights and structures, cross-link densities, and other characteristicsoffer a broad spectrum of product properties. For example, one-componentproducts are available with elongations as high as 1000%. Typicalproperties of representative cured RTV silicone rubbers are shown inTables 13 and 14. TABLE 13 Thermal Properties of Cured SiliconeElastomers One Component Two Components General Construction AdhesiveMolding Property Purpose Sealant Sealant Compound Hardness, Shore A, 3022 50 60 durometer Tensile Strength, MPa 2.4 1.0 3.4 5.5 Elongation, %400 850 200 220 Tear Strength, J/cm² 0.80 0.35 0.52 1.75

[0113] TABLE 14 Thermal Properties of Cured Silicone Elastomers PropertyTypical Range Useful temperature range, ° C. −110 to 200 with thermalstabilizers −110 to 250 Thermal conductivity, W/(m · K) 1.7-3.4Coefficient of thermal expansion, per ° C. 3.5 × 10⁻⁵

[0114] The one-component RTV silicone rubbers are in some instances,preferred for use in the present invention golf balls, particularly forone or more interior layers. Such layers may be formed by encapsulatingthe core with an RTV silicone rubber material. Many formulations provideself-bonding to most metals, glass, ceramics, concrete, and plastics.For example, bonds to aluminum with >1.38 MPa (200 psi) shear strengthand 0.35 J/cm² (20 lbf/in.) tear strength are obtainable. Bonding can beimproved by applying a primer to the substrate. These primers aresolutions of reactive silanes or resins that dry (cure) on thesubstrate, leaving a modified silicone bondable surface. Bond strengthdevelops as the RTV cure progresses.

[0115] The two-component RTV silicone rubbers are commercially availablein a wide range of initial viscosities, from as low as an easilypourable 100-mm²/s material to as high as the stiff paste like materialsof over 1,000,000 mm²/s at 25° C. Curing system, polymer molecularweight and structure, cross-link density, filler, and additives can bevaried and combined, giving a group of products whose properties cover awider range than that encompassed by the one-component products. Thehighest strength RTV rubbers are provided by two-component RTVtechnology. On the other hand, products that cure to a mere gel are alsoavailable. Unfilled resin-reinforced compositions can provide opticalclarity. Polymers with phenyl, trifluoropropyl, cyanoethyl, or othersubstituents can be used with, or in place of, polydimethylsiloxanes forlow temperature-, heat-, radiation-, and solvent-resistant elastomers.

[0116] In one-component formulations that rely for cure on the reactionbetween a reactive cross-linking agent and atmospheric moisture, theingredients must be thoroughly dried, or a drying step must be includedin the compounding cycle. As more filler is added during compounding,the resistance to mixing tends to peak until “wetting-in” is reached.The moisture-sensitive cross-linking agent is usually added last.However, this step can be performed separately. When the uncatalyzedbase compound and cross-linking agent are mixed, the effective viscositysometimes passes through a maximum. As the early chemical interactionsare resolved, a typical consistency is obtained. Allowance for elevatedeffective in-process viscosities must be made when mixing equipment isspecified. Silica-reinforced uncatalyzed base compounds harden (developstructure) on storage, and the addition of catalyst should not bedelayed.

[0117] For two-component formulations, each part may contain varyingproportions of filler and polymer. The second part contains the curingcatalyst and possibly the cross-linking agent and pigments. By properdesign of the compound, the proportions of first and second parts to beused may be adjusted for convenient handling and metering. Typically,from about 1 to 20 parts of the first part are typically used per partof the second.

[0118] Many commercially available two-component RTV elastomers can beadvantageously cured at 50-150° C., depending on the product andintended use, but RTV is characteristic. Hydrosilation-curing RTVcompositions can be modified with inhibitors to become heat-curingsystems.

[0119] Unlike RTV compositions, most heat-curing silicone rubbers arebased on high molecular weight polymer gums. Gums, fillers, andadditives can be mixed in dough mixers or Banbury mills. Catalysts areadded on water-cooled rubber mills, which can be used for the completeprocess in small-scale operations.

[0120] Silicone rubbers are commercially available as gums,filler-reinforced gums, dispersions, and uncatalyzed and catalyzedcompounds. Dispersions or pastes may be stirred with solvents such asxylene. The following types of gums are commercially available: generalpurpose (methyl and vinyl), high and low temperature (phenyl, methyl,and vinyl), low compression set (methyl and vinyl), low shrink(devolatilized), and solvent resistant (fluorosilicone); properties areshown in Table 15.

[0121] The tensile strength of cured dimethylsilicone rubber gum is onlyabout 0.34 MPa (50 psi). Finely divided silicas are used forreinforcement. Other common fillers include mined silica, titaniumdioxide, calcium carbonate, and iron (III) oxide. Crystallizing segmentsincorporated into the polymer also serve as reinforcement. For example,block copolymers containing silphenylene segments,(CH₃)₂SiC₆H₄Si(CH₃)₂O_(n), may have cured gum tensile strengths of6.8-18.6 MPa (1000-2700 psi). TABLE 15 Properties of Silicone GumsT_(g), Williams Plasticity Type Density d²⁵, g/cm³ ° C. (ASTM D926)(CH₃)₂SiO 0.98 −123  95-125 CH₃(C₆H₅)SiO 0.98 −113 135-180CH₃(CF₃CH₂CH₂)SiO 1.25 −65

[0122] Consistencies of uncured rubber mixtures range from a tough puttyto a hard deformable plastic. Those containing reinforcing fillers tendto stiffen, i.e., develop structure, on storage. Additives, such aswater, diphenylsilanediol, dimethylpinacoxysilane, or silicone fluids,inhibit stiffening.

[0123] The properties of fabricated rubber depend on the gum, filler,catalyst, additives, and solvents and their proportions. A high fillercontent increases hardness and solvent resistance and reduceselongation. The properties also depend on the thoroughness of mixing andthe degree of wetting of the filler by the gum. The properties change ascure progresses and are stabilized by devolatilization. The propertiesmay also be affected by the environment and aging.

[0124] Before being used, silicone rubber mixtures are preferablyfreshened. Catalyst is added, and the mixture is freshly milled onrubber mills until the components band into smooth continuous sheetsthat are easily worked. Specific or custom mixtures are prepared bysuppliers for particular product applications. A formula is designed toachieve some special operating or processing requirement, andformulations are classified accordingly as set forth below in Table 16.TABLE 16 Properties of Silicone Rubber Classes Useful TensileCompression Temperature Tear Hardness, Strength, set at 150° C. Range, °C. Strength, Class Durometer MPa Elongation % for 22 h, % MinimumMaximum J/cm² General purpose 40-80 4.8-7.0 100-400 −60 260 0.9 Lowcompression set 50-80 4.8-7.0  80-400 15-50 −60 260 0.9 Extreme lowtemperature 25-80  5.5-10.3 150-600 10-15 −100 260 3.1 Extreme hightemperature 40-80 4.8-7.6 200-500 20-50 −60 315 Wire and cable 50-80 4.1-10.3 100-500 10-40 −100 260 Solvent resistant 50-60 5.8-7.0 170-22520-50 −68 232 1.3 High strength flame retardant 40-50  9.6-11.0 500-70020-30 2.8-3.8

[0125] Silicone rubbers are cured by several mechanisms. Forhydrosilation cure, high molecular weight polymers (gums) with vinylfunctionality are combined with fluid hydride-functional cross-linkingagents. The catalyst, such as a soluble platinum compound, is added withan inhibitor to prevent cure initiation before heating.

[0126] Silicone rubber is usually cured by heating the reinforcedpolymer with a free-radical generator, e.g., benzoyl peroxide.

[0127] Cure is also effected by gamma or high energy electron radiation,which causes scission of all types of bonds, including Si—O; theimportant cure reactions and those involving Si—C and C—H. Hydrogen,methane, and ethane evolve, and bridges between chains are formed byrecombination of the radicals generated. These bridges includeSi—CH₂—Si,Si—Si, and perhaps Si—CH₂CH₂—Si. An absorbed dose of770-1300C/kg (3×10⁶ to 5×10⁶ roentgen) is typically required foreffective cure. Radiation cure can be used for thick sections, but highenergy electrons penetrate to a depth of only a few millimeters.

[0128] Freshly mixed silicone rubber compounds are usually molded at100-180° C. and 5.5-10.3 MPa (800-1500 psi). Under these conditions,thermal cure can be completed in minutes. The molds are usuallylubricated with a 1-2 wt % aqueous solution of a household detergent.Final properties can be developed by oven curing or by continuous steamvulcanization.

[0129] For bonding silicone rubber to other materials, such as aninterior layer or core in the golf balls of the present invention,primers are preferably used, including silicate esters, silicone pastes,silicone resins, or reactive silanes. After evaporation of solvent andsetting or cure of the primed surface, the rubber compounds are appliedand cured under pressure. Self-bonding silicone rubber stocks require noprimer.

[0130] Silicone rubber is compounded in dough mixers, Banbury mixers,two-roll rubber mills, various types of change-can mixers, andcontinuous compounders. Large vertical Banbury mixer systems are usedfor high volume semicontinuous production of dry (but not overly tacky)compounds; tackiness can create problems in unloading. The basic processrequirements are similar in nearly all applications: addition of gums,fillers, process aids, pigments, and catalysts in the prescribed order;breakdown of agglomerates in the fillers; uniform dispersion of fillerin the gum; and control of temperature and, in some cases, pressure forretention or removal of volatile ingredients and prevention of prematurecure.

[0131] The properties of cured silicone elastomers are temperaturedependent. For example, Young's modulus decreases from about 10,000 to200 MPa (145×10⁴ to 2.9×10⁴ psi) between −50 and 25° C. and remainsfairly constant to 260° C. Tensile strength decreases from approximately6.9 MPa (1000 psi) at 0° C. to 2.1 MPa (300 psi) at 300° C. The thermalconductivity of silicone rubber is usually about 1.5-4 W/(m·K) andincreases with increasing filler content.

[0132] Silicone rubber (gum) films are permeable to gases andhydrocarbons; they are about 10-20 times as permeable as organicpolymers. Water diffuses through lightly cross-linked gum as monomer,dimer, and trimer, with diffusion coefficients of 1.5, 3.6, and3.1×10⁻⁵, respectively, at 65° C. Silicone rubber compounds are alsopermeable to gases. Cross-linking and fillers reduce permeability.

[0133] Solvents diffuse into silicone rubber and swell, soften, and mayresult in weakening of the rubber. The degree of swelling depends on thesolvent and has been correlated with the solubility parameters ofsolvent and rubber. The correlation is improved if electrostaticinteractions are considered.

[0134] Silicone elastomers appear completely hydrophobic to liquidwater. Aqueous solutions interact with silicone rubber with varyingeffects. Water itself has little effect, although at higher temperaturesit causes softening and weakening. If the rubber is heated with water ina sealed environment, it is converted to a sticky polymer.

[0135] In contrast to the silicone fluids and elastomers, siliconeresins contain Si atoms with no or only one organic substituent. Theyare therefore crosslinkable to harder and stiffer compounds than theelastomers, but many must be handled in solution to prevent prematurecure. They are, in fact, usually made by hydrolysis of the desiredchlorosilane blend in the presence of a solvent such as mineral spirits,butyl acetate, toluene, or xylene. These materials are usually curedwith metal soaps or amines.

[0136] As noted, silicone resins are highly cross-linked siloxanesystems. The cross-linking components are introduced as trifunctional ortetrafunctional silanes in the first stage of manufacture or processing.For example, a solution of CH₃SiCl₃, (CH₃)₂,SiCl₂, C₆H₅SiCl₃, and(C₆H₅)₂SiCl₂ or CH₃(C₆H₅)SiCl₂ in toluene is hydrolyzed to form acomplex copolymer mixture, which remains in solution in toluene. Theaqueous hydrochloric acid is separated, and the resin solution is washedand heated in the presence of a mild condensation catalyst to adapt(body) the resin to the proper viscosity and cure time. It is finallyadjusted to specifications by distilling or adding solvents. Theproperties of the resins depend on the choice of chlorosilanes, thedegree of cure, and the processing conditions.

[0137] The chlorosilanes for a particular resin formulation determineits characteristics. Monomethyl-, dimethyl-, monophenyl-, diphenyl-,methyl-phenyl-, monovinyl-, and methylvinylchlorosilanes, together withsilicon tetrachloride, are typical chlorosilanes. Prediction of specificresin properties as a function of composition is difficult sinceprocessing and cure influence the final molecular configuration andrelated characteristics. However, some generalizations can be made:trifunctional siloxy units produce harder, less flexible resins, whichare frequently immiscible with organic polymers; difunctional siloxyunits increase softness and flexibility, and phenylsiloxanes are moremiscible with organic polymers than methylsiloxanes and produce resinsthat are less brittle and have superior thermal resistance. Alkyl groupsother than methyl also increase the compatibility with other organicmaterials. The effects of silanes on the properties of a film are shownin Table 17. Properties of these silanes vary considerably. Some resinsare soft and flexible, and others are hard and glassy. Processingconditions vary from hydrolysis in strong acid to dilute acid orbuffered aqueous systems. Alkoxysilanes can also be used to avoid acidconditions. Solvent, temperature, concentration, and catalyst forbodying and curing affect the result. TABLE 17 Effect of Silanes on theProperties of Silicone Resin Films Property CH₃SiCl₃ C₆H₅SiCl₃(CH₃)₂SiCl₂ (C₆H₅)₂SiCl₉ CH₃(C₆H₅)SiCl₉ Hardiness increase increasedecrease decrease decrease Brittleness increase great increase decreasedecrease decrease Stiffness increase increase decrease decrease decreaseToughness increase Increase decrease decrease decrease Cure Speed muchfaster some increase slower much slower slower Tack decrease somedecrease increase increase increase

[0138] Most silicone resin products require heat and catalysts forcuring. During the life of the product, curing continues, and propertieschange with time. For this reason, silicone resins exhibiting thischaracteristic are generally less preferred than silicone elastomers andrubbers described herein.

[0139] Silicone resins are cured through the formation of siloxanelinkages by the condensation of silanols. This is a continuation of theoverall condensation process by which the resin is prepared. Ascondensation continues, the rate decreases because of lower silanolconcentration, increased steric hindrance, and reduced mobility. Forfinal cure, therefore, the reaction must be accelerated by heat andcatalyst. Even so, some silanols remain, and slow cure continues for thelife of the resin. The reaction is reversible, and water must be removedfrom the system to permit a high degree of cure. Many substancescatalyze silanol condensation, including acids and bases; solubleorganic salts of lead, cobalt, tin, iron, and other metals and organotincompounds, e.g., dibutyl tin dilaurate, orN,N,N′,N′-tetramethylguanidine salts.

[0140] Silicone resins based on hydrosilation cure have also beendeveloped. These materials cure by addition reactions and are similar incomposition to hydrosilation-curing elastomers, however are generallymore highly cross-linked.

[0141] Silicone resins change little on exposure to humidity, heat, andsunlight. Weather resistance is also exhibited by silicone—organiccopolymers and blends, provided the silicone content is high enough.

[0142] A variety of commercially available silicone resins may beutilized in the preferred embodiment golf balls. For example, siliconeresins can be obtained from Dow Corning Corp., Midland, Mich.; GESilicones, Waterford, N.Y.; Gelest Inc., Tullytown, Pa.; WackerSilicones, Adrian, Mich.; and Shin-Etsu Chemical Co., Ltd, Tokyo 100,Japan.

[0143] A particularly preferred commercial supplier of silicone resin isShin-Etsu. Shin-Etsu offers a two-component, high strength moldingcompound under the designation KE 1300, that provides excellent resinresistance and will not shrink when cured at room temperature.

[0144] KE 1300 features high tear strength. It is ideal for intricatemolds, or applications where tearing or ripping. of a mold is a concern.KE 1300 is available in a T is (translucent) and a white version.Properties and mold life will be the same with both. The translucentversion (KE 1300T) is very useful for applications where visual sightingof the master or where identification of voids is needed. KE1300T and KE1300 (white) are preferred whenever resistance. to attack by epoxies,polyesters and urethanes and high tear strength in a medium modulusmaterial is required.

[0145] Whenever Catalyst 1300L-3 is used to cure KE 1300 or KE 1300T, alower modulus material results without seriously effecting tearstrength. This is appropriate for those applications where demolding isa problem due to deep undercuts or thick cross-sections.

[0146] Other suitable silicone resins available from Shin-Etsu are setforth below in Table 18. The noted KE 1402, SES 412, and KE 10 are allcondensation cure products. The noted KE 1300T, KE 1300, KE 1310ST, KE1310S, KE 1600, and KE 1604 are all addition cure products. Theseaddition cure products can be heat accelerated if a faster cure isdesired. For example, a heat cure for 2 hours at 60° C. can be performedat 1 hour at 85° C. TABLE 18 General Characteristics of CommerciallyAvailable Silicone Compositions Product Color Description Pot Life (Hrs)Catalyst KE 1402 Pink Low durometer, high 1.5 CAT 1402 strengthinhibition resistant SES 412 White Medium durometer, 0.5 CAT RM lowviscosity, general purpose KE 10 Off-white High durometer, low 1.0 CATRA viscosity, general purpose KE 1300T Translucent Low durometer, 1.5CAT 1300L-3 high strength KE 1300T Translucent Medium durometer, 1.5 CAT1300 high strength KE 1300 White Medium durometer, 1.5 CAT 1300 highstrength, opaque KE 1310ST Translucent Premium strength, 2.0 CAT 1310longest mold life KE 1310S White Premium strength, 2.0 CAT 1310 longestmold life, opaque KE 1600 Off-white Medium durometer, 2.0 CAT 1300general purpose KE 1604 Blue High durometer, 2.0 CAT 1604 generalpurpose KE 1604 Off-white High durometer, 2.0 CAT 1604T general purpose,neutral color Physical Properties of Commercially Available SiliconeCompositions Initial Mixed Hardness Tensile Linear Tear ViscosityDurometer Strength Elongation Shrinkage Strength Specific Product(poise) (Shore-A) (psi) % (%) (ppli) Gravity KE 1402 600 25 600 400 0.4120 1.10 SES 412 100 40 355 160 0.2 45 1.30 KE 10 300 55 480 150 0.1 451.15 KE 1300T 1000 30 630 400 <0.1 110 1.11 KE 1300T 1000 40 800 300<0.1 125 1.11 KE 1300 1000 40 800 300 <0.1 125 1.11 KE 1310ST 840 40 850340 <0.1 140 1.07 KE 1310S 840 40 850 340 <0.1 140 1.07 KE 1600 1700 501000 200 <0.1 80 1.26 KE 1604 1000 60 1100 170 <0.1 95 1.26 KE 1604 100060 1100 170 <0.1 95 1.26 Curing Properties of Commercially AvailableSilicone Resins Product Base Curing Agent Ratio by WT. Curing Hr/° C. KE1402  10:1 24/25 SES 412 100:0.5 24/25 KE 10 100:2.5 24/25 KE 1300T 10:1 24/25 KE 1300T  10:1 24/25 KE 1300  10:1 24/25 KE 1310ST  10:124/25 KE 1310S  10:1 24/25 KE 1600  10:1 24/25 KE 1604  10:1 24/25 KE1604  10:1 24/25

[0147] When utilizing a two part, addition cure, silicone resin, typicalproperties of the components and cured compositions are set forth belowin Table 19 as follows: TABLE 19 Typical Properties of Two Part,Silicone Resins Part A Part B Mixed A/B Appearance Milky-WhiteMilky-White Milky-White Translucent Translucent Translucent SpecificGravity, @ 25° 1.08 + 0.04 1.08 + 0.04 1.08 + 0.04 Viscosity, @ 25°500-1,000P 1-50P  500 ± 250P Cured Properties (Cure Condition: 15 min. @150° C.): Hardness, Shore 00   70 ± 15 Tensile Strength, psi  450 ± 150Elongation, %  500 ± 150

[0148] Preferably, the silicone material utilized in the preferredembodiment golf balls exhibits, upon curing, a Shore 00 hardness of fromabout 55 to about 100; a tensile strength of from about 300 psi to about600 psi; and an elongation of from about 350% to about 650%.

[0149] As noted, the present invention golf balls may comprise one ormore interior layers comprising one or more silicone materials.Referring to FIG. 3, a preferred embodiment golf ball 20 is illustratedcomprising a core 22 formed from a material as described herein, and aninterior layer 24 formed from one or more silicone material(s). Theinterior layer 24 is disposed between the core 22 and an outer layer 26.The outer layer 26 may be in the form of the previously describedmultilayer cover 12.

[0150] In another preferred embodiment, the present invention provides agolf ball 30 as shown in FIG. 4. The golf ball 30 comprises a core 32,formed from a material as described herein, and two inner layers, suchas 34 and 36. Either or both of the inner layers 34 and 36 may be formedfrom a silicone material. The golf ball 30 may further comprise an outerlayer 38 similar to the outermost multilayer cover 12.

[0151] In yet another preferred embodiment, the present inventionprovides a golf ball 40 as shown in FIG. 5. The golf ball 40 comprises acore 42, formed from a material as described herein, and three or moreinner layers such as layers 44, 46, and 48, that may be formed from asilicone material. The golf ball 40 may further comprise an outermostlayer 49 similar to the previously described multilayer cover 12.

[0152] Although not wishing to be bound to any particular dimensions,the present inventors have determined that the one or more siliconelayers preferably have the following dimensions and characteristics.When utilized in conjunction with a core of at least about 1.20 inchesin diameter or greater, the total thickness of the silicone layers is atleast about 0.020 inches or greater. The golf balls may utilize one ormore silicone layers, however it is preferred to provide at least two ormore. If the silicone layers are used in combination with one or morelayers of a non-silicone composition, it is preferred that the thicknessof the non-silicone layers be at least about 0.020 inches or greater.Examples of such non-silicone materials include, but are not limited to,relatively hard, resilient materials such as ionomers, nylons,thermoplastic urethanes, and hytrels for instance. The minimum totalthickness of all layers within the preferred embodiment golf balls isabout 0.040 inches. The preferred total thickness of all the siliconelayers is about 0.050 inches.

[0153] As previously noted, the preferred embodiment golf balls of thepresent invention may further comprise a core comprising a siliconecomposition. Such material is preferably selected from the previouslynoted silicone materials. A particularly preferred core composition isbased upon blends of ionomers as described herein and a commerciallyavailable silicone rubber, Dow Corning Silastic rubber WC-50. SilasticWC-50 comprises a low level of vinyl groups and has a specific gravityof about 1.15 and a brittleness temperature of about −39° C.

[0154] Referring to FIGS. 6-8, several additional preferred embodimentgolf balls are illustrated comprising cores including a siliconematerial and one or more inner layers comprising materials describedherein. FIG. 6 illustrates a preferred embodiment golf ball 50comprising a core 52 including a silicone material, an inner layer 54,and an outer cover 56. The outer cover 56 may be in the form of thepreviously described multilayer cover 12.

[0155] The invention also provides another preferred embodiment golfball 60 illustrated in FIG. 7 comprising a core 62 formed from asilicone material, a first inner layer 64, a second inner layer 66, andan outer cover 68. The outer cover 68 may be in the form of thepreviously described multilayer cover 12.

[0156]FIG. 8 depicts another preferred embodiment golf ball 70comprising a core 72, a plurality of inner layers 74, 76, and 78, and anouter cover 79. The core 72 comprises a silicone material. The outercover 79 may be in the form of the previously described multilayer cover12.

[0157] The core has a preferred set of characteristics as follows. Thesilicone core is preferably from about 1.10 inches to about 1.60 inchesin diameter. When utilizing a silicone composition core, the mantle (orone or more interior layers) thickness is from about 0.020 inches toabout 0.145 inches. And, the cover thickness is from about 0.020 inchesto about 0.145 inches. The ball diameter is preferably from about 1.68inches to about 1.75 inches or more in diameter. When utilizing asilicone core, the golf ball preferably includes at least two or morelayers. The mantle and/or cover. layers may be formed from a relativelyhard resilient materials such as for example, ionomers, nylons,polyurethanes, polyester elastomers, etc.

[0158] Moreover, the present invention provides golf balls having both acore formed from a silicone material and one or more inner layers formedfrom a silicone material. The configuration or structure of such ballsmay be as depicted in FIGS. 1-8.

[0159] In preparing preferred golf balls in accordance with the presentinvention, a hard inner cover layer is molded (for instance by injectionmolding or by compression molding) about a core (preferably a solidcore). A comparatively softer outer layer is molded over the innerlayer. The conventional solid core is about 1.545 inches in diameter,although it can range from about 1.495 to about 1.575 inches.Conventional solid cores are typically compression molded from a slug ofuncured or lightly cured elastomer composition comprising a high ciscontent polybutadiene and a metal salt of an α, β, ethylenicallyunsaturated carboxylic acid such as zinc mono or diacrylate ormethacrylate. To achieve higher coefficients of restitution in the core,the manufacturer may include fillers such as small amounts of a metaloxide such as zinc oxide. In addition, larger amounts of metal oxidethan those that are needed to achieve the desired coefficient are oftenincluded in conventional cores in order to increase the core weight sothat the finished ball more closely approaches the U.S.G.A. upper weightlimit of 1.620 ounces. Other materials may be used in the corecomposition including compatible rubbers or ionomers, and low molecularweight fatty acids such as stearic acid. Free radical initiators such asperoxides are admixed with the core composition so that on theapplication of heat and pressure, a complex curing cross-linkingreaction takes place.

[0160] The inner cover layer, such as layer 14 of the multilayer cover12, which may be molded over a core or another interior layer, is about0.100 inches to about 0.010 inches in thickness, preferably about 0.0375inches thick. The outer cover layer, such as layer 16 of the multilayercover 12, is about 0.010 inches to about 0.050 inches in thickness,preferably 0.0300 inches thick. Together, the core, the inner coverlayer and the outer cover layer combine to form a ball having a diameterof 1.680 inches or more, the minimum diameter permitted by the rules ofthe United States Golf Association and weighing about 1.620 ounces.

[0161] Additional materials may be added to the cover compositions (bothinner and outer cover layer) of the present invention including pigments(For example, Ultramarine Blue sold by Whitaker, Clark and Daniels ofSouth Plainsfield, N.J.) (see U.S. Pat. No. 4,679,795); and pigmentssuch as titanium dioxide, zinc oxide, barium sulfate and zinc sulfate;optical brighteners; and UV absorbers; antibxidants; antistatic agents;and stabilizers. Further, the cover compositions of the presentinvention may also contain softening agents, such as plasticizers,processing aids, etc., and reinforcing material such as glass fibers andinorganic fillers, as long as the desired properties produced by thegolf ball covers are not impaired.

[0162] As previously described with regard to silicone elastomers, itmay, in some instances, be preferred to incorporate one or more filleragents in the one or more inner layers comprising silicone materials. Itmay also be desirable to incorporate such agents in a silicone core.Incorporating such agents may serve to reinforce that resulting siliconecomposite material, and/or alter other physical properties of the layerand/or core. The use of such agents may serve to increase, or in somecases, decrease, one or more of the following properties: hardness,strength, rigidity, elasticity, and density. With regard to increasingthe density of a silicone material utilized in the present inventiongolf balls, it is particularly preferred to incorporate such agents,particularly those having a relatively high density, in a silicone layerin order to increase the weight and moment inertia of the ball. Examplesof suitable filler and/or weighting agents include, but are not limitedto, particulate silica; fumed silica; particulate aluminum silicate orother similar materials; carbon black or graphite in fiber or powderform; boron in powder or salt form; Kevlar in fiber form; cotton flock;nylon flock; glass in nearly any form; ceramic materials in nearly anyform; Cermet, i.e., ceramic-metal, materials in any form; Hi-Sil; andmetals in any form. Other compounds may be used such as calciumcarbonate, various clays, and plastics such as ground polypropylene.Regarding the use of metals, nearly any metal, preferably in fineparticulate form, may be utilized. Examples of suitable metals includealuminum, magnesium, beryllium, iron, titanium, tungsten, copper, zinc,and alloys or oxides thereof. Examples of such alloys include brass orbronze. It is also contemplated to utilize other materials as filler,weighting, or reinforcing agents such as metal stearate salts, siliconcarbide, ceramic whiskers, and combinations thereof. Furthermore, thepresent inventors have identified several preferred metallic compoundsand combinations of materials for incorporation in the one or moresilicone material layers and/or core. These preferred combinationsinclude, but are not limited to: beryllium oxide, aluminum oxide,titanium dioxide and graphite powder, titanium dioxide and ceramicpowder, and combinations thereof.

[0163] The various cover composition layers of the present invention maybe produced according to conventional melt blending procedures. In thecase of the outer cover layer, when a blend of hard and soft, low acidionomer resins are utilized, the hard ionomer resins are blended withthe soft ionomeric resins and with a master batch containing the desiredadditives in a Banbury mixer, two-roll mill, or extruder prior tomolding. The blended composition is then formed into slabs andmaintained in such a state until molding is desired. Alternatively, asimple dry blend of the pelletized or granulated resins and color masterbatch may be prepared and fed directly into the injection moldingmachine where homogenization occurs in the mixing section of the barrelprior to injection into the mold. If necessary, further additives suchas an inorganic filler, etc., may be added and uniformly mixed beforeinitiation of the molding process. A similar process is utilized toformulate the high acid ionomer resin compositions used to produce theinner cover layer.

[0164] The golf balls of the present invention can be produced, at leastin part, by molding processes currently known in the golf ball art.Specifically, the golf balls can be produced by injection molding orcompression molding the inner cover layer about wound or solid moldedcores to produce an intermediate golf ball having a diameter of about1.50 to 1.67 inches, preferably about 1.620 inches. The outer layer issubsequently molded over the inner layer to produce a golf ball having adiameter of 1.680 inches or more. Although either solid cores or woundcores can be used in the present invention, as a result of their lowercost and superior performance, solid molded cores are preferred overwound cores.

[0165] In compression molding, the inner cover composition is formed viainjection at about 380° F. to about 450° F. into smooth surfacedhemispherical shells which are then positioned around the core in a moldhaving the desired inner cover thickness and subjected to compressionmolding at 200° F. to 300° F. For about 2 to 10 minutes, followed bycooling at 50° F. to 70° F. For about 2 to 7 minutes to fuse the shellstogether to form a unitary intermediate ball. In addition, theintermediate balls may be produced by injection molding wherein theinner cover layer is injected directly around the core placed at the.center of an intermediate ball mold for a period of time in a moldtemperature of from 50° F. to about 100° F. Subsequently, the outercover layer is molded about the core and the inner layer by similarcompression or injection molding techniques to form a dimpled golf ballof a diameter of 1.680 inches or more.

[0166] Molding or otherwise forming the silicone layers and/or core mayfurther entail additional considerations such as follows. A siliconemantle could be applied directly over a core, either a core comprising asilicone composition or as otherwise described herein, or sandwichedbetween two or more non-silicone layers. There are severalconsiderations or practices that may be followed in a preferredtechnique for molding a core and/or one or more layers comprising asilicone material.

[0167] A vessel which is pressure-rated and of adequate size to degasthe desired amount of silicone material is preferably employed. A vacuumsystem is used to pull or otherwise remove air induced during the mixingcycle from the material. This process insures a void-free moldedcomponent.

[0168] An oven can be used to accelerate the cure rate of the siliconematerial. Oven temperature should not exceed 200° C. (396° F.). Mostsilicone molded materials should not be exposed to elevated temperaturesfor more than 2 hours.

[0169] Certain chemicals, curing agents, plasticizers and materials caninhibit cure. The most common are: organo-tin and other organo-metalliccompounds; silicone rubber containing organo-tin catalyst; sulfur,polysulfides, polysulfones and other sulfur-containing materials;amines, urethanes, and amine containing materials; and unsaturatedhydrocarbon plasticizers.

[0170] Should a substrate or material be a possible cause of inhibition,it is best to test a small sample for compatibility with the elastomer.The presence of liquid or uncured product at the,interface between thesuspect substrate and the cured elastomer would indicate cureinhibition.

[0171] After molding, the golf balls produced may undergo variousfurther processing steps such as buffing, painting and marking asdisclosed in U.S. Pat. No. 4,911,451.

[0172] The resulting golf ball produced from the high acid ionomer resininner layer and the relatively softer, low flexural modulus outer layerprovide for an improved multi-layer golf ball which provides fordesirable coefficient of restitution and durability properties while atthe same time offering the feel and spin characteristics associated withsoft balata and balata-like covers of the prior art.

[0173] Additional details of the chemistry and processing of siliconematerials are provided in “Encyclopedia of Polymer Science andEngineering,” Vol. 15, Second Edition, pages 204-308, by B. Hardman andA. Torkelson, herein incorporated by reference.

[0174] The present invention is further illustrated by the followingexamples in which the parts of the specific ingredients are by weight.It is to be understood that the present invention is not limited to theexamples, and various changes and modifications may be made in theinvention without departing from the spirit and scope thereof.

EXAMPLES

[0175] Several intermediate balls (cores plus inner cover layers) wereprepared in accordance with molding procedures described above. Theinner cover compositions were molded around 1.545 inch diameter coresweighing 36.5 grams such that the inner cover had a wall thickness ofabout 0.0675 inches, with the overall ball measuring about 1.680 inchesin diameter.

[0176] The cores utilized in the examples were comprised of thefollowing ingredients: high cis-polybutadiene, zinc diacrylate, zincoxide, zinc stearate, peroxide, calcium carbonate, etc. The molded coresexhibited Riehle compressions of about 60 and C.O.R. values of about0.800. A representative formulation of the molded cores is set forthbelow in Table 20: TABLE 20 Representative Formulation For Molded CoreMATERIAL WEIGHT BR-1220 (high cis- 70.70 polybutadiene) Taktene 220(high cis- 29.30 polybutadiene) React Rite ZDA (zinc 31.14 diacrylate)Zinc Oxide 6.23 Zinc Stearate 20.15 Limestone 17.58 Ground Flash 20.15(20-40 Mesh) Blue Master batch .012 Luperco 231XL .89 or Trigonox 29/40Papi 94 .50

[0177] The inner cover compositions designated herein as compositionsA-E utilized to formulate the intermediate balls are set forth in Table21 below. The resulting molded intermediate balls were tested todetermine the individual compression (Riehle), C.O.R., Shore C hardness,spin rate and cut resistance properties. These results are also setforth in Table 8 below.

[0178] The data of these examples are the average of twelve intermediateballs produced for each example. The properties were measured accordingto the following parameters:

[0179] Coefficient of restitution (C.O.R.) was measured by firing theresulting golf ball in an air canon at a velocity of 125 feet per secondagainst a steel plate positioned 12 feet from the muzzle of the canon.The rebound velocity was then measured. The rebound velocity was dividedby the forward velocity to give a coefficient of restitution.

[0180] Shore hardness was measured in accordance with ASTM test 2240.

[0181] Cut resistance was measured in accordance with the followingprocedure: A golf ball is fired at 135 feet per second against theleading edge of a pitching wedge wherein the leading edge radius is{fraction (1/32)} inch, the loft angle is 51 degrees, the sole radius is2.5 inches and the bounce angle is 7 degrees.

[0182] The cut resistance of the balls tested herein was evaluated on ascale of 1 to 5. The number 1 represents a cut that extends completelythrough the cover to the core. A 2 represents a cut that does not extendcompletely through the cover but that does break the surface. A 3 doesnot break the surface of the cover but does leave a permanent dent. A 4leaves only a slight crease which is permanent but not as severe as 3. A5 represents virtually no visible indentation or damage of any sort.

[0183] The spin rate of the golf ball was measured by striking theresulting golf balls with a pitching wedge or 9 iron wherein the clubhead speed is about 105 feet per second and the ball is launched at anangle of 26 to 34 degrees with an initial velocity of about 110 to 115feet per second. The spin rate was measured by observing the rotation ofthe ball in flight using stop action Strobe photography.

[0184] Initial velocity is the velocity of a ball when struck at ahammer speed of 143.8 feet per second in accordance with a test asprescribed by the U.S.G.A.

[0185] As will be noted, compositions A, B and C include high acidionomeric resins, with composition B further including zinc stearate.Composition D represents the inner layer (i.e. Surlyn 1605) used in U.S.Pat. No. 4,431,193. Composition E provides a hard, low acid ionomericresin.

[0186] The purpose behind producing and testing the balls of Table 21was to provide a subsequent comparison in properties with themulti-layer golf balls of the present invention. TABLE 21 MoldedIntermediate Golf Balls A B C D E Ingredients of Inner Cover Com-positions Iotek 959 50 50 — — — Iotek 960 50 50 — — — Zinc Stearate — 50— — — Surlyn 8162 — — 75 — — Surlyn 8422 — — 25 — — Surlyn 1605 — — —100 — Iotek 7030 — — — — 50 Iotek 8000 — — — — 50 Properties of MoldedIntermediate Balls Compression 58 58 60 63 62 C.O.R. .811 .810 .807 .793.801 Shore C 98 98 97 96 96 Hardness Spin Rate 7,367 6,250 7,903 8,3377,956 (R.P.M.) Cut 4-5 4-5 4-5 4-5 4-5 Resistance

[0187] As shown in Table 21 above, the high acid ionomer resin innercover layer (molded intermediate balls A-C) have lower spin rates andexhibit substantially higher resiliency characteristics than the lowacid ionomer resin based inner cover layers of balls D and E.

[0188] Multi-layer balls in accordance with the present invention werethen prepared. Specifically, the inner cover compositions used toproduce intermediate golf balls from Table 21 were molded over the solidcores to a thickness of about 0.0375 inches, thus forming the innerlayer. The diameter of the solid core with the inner layer measuredabout 1.620 inches. Alternatively, the intermediate golf balls of Table21 were ground down using a centerless grinding machine to a size of1.620 inches in diameter to produce an inner cover layer of 0.0375inches.

[0189] The size of 1.620 inches was determined after attempting to moldthe outer cover layer to various sizes (1.600″, 1.610″, 1.620″, 1.630″and 1.640″) of intermediate (core plus inner layer) balls. It wasdetermined that 1.620″ was about the largest “intermediate” ball (i.e.,core plus inner layer) which could be easily molded over with the softouter layer materials of choice. The goal herein was to use as thin anouter layer as necessary to achieve the desired playabilitycharacteristics while minimizing the cost of the more expensive outermaterials. However, with a larger diameter final golf ball and/or if thecover is compression molded, a thinner cover becomes feasible.

[0190] With the above in mind, an outer cover layer composition wasblended together in accordance with conventional blending techniques.The outer layer composition used For this portion of the example is arelatively soft cover composition such as those listed in U.S. Pat. No.5,120,791. An example of such a soft cover composition is a 45% soft/55%hard low acid ionomer blend designated by the inventor as “TE-90”. Thecomposition of TE-90 is set forth below in Table 22 as follows: TABLE 22Outer Cover Layer Composition TE-90 Iotek 8000 22.7 weight % Iotek 703022.7 weight % Iotek 7520 45.0 weight % White MB¹  9.6 weight %

[0191] The above outer layer composition was molded around each of the1.620 diameter intermediate balls comprising a core plus one ofcompositions A-D, respectively. In addition, for comparison purposes,Surlyn® 1855 (new Surlyn® 9020), the cover composition of the '193patent, was molded about the inner layer of composition D (theintermediate ball representative of the '193 patent). The outer layerTE-90 was molded to a thickness of approximately 0.030 inches to producea golf ball of approximately 1.680 inches in diameter. The. resultingballs (a dozen balls For each example) were tested and the variousproperties thereof are set forth in Table 23 as follows: TABLE 23Finished Balls 1 2 3 4 5 Ingredients: Inner Cover Composition A B C D DOuter Cover Composition TE-90 TE-90 TE-90 TE-90 Surlyn ® 9020 Propertiesof Molded Finished Balls: Compression   63   63   69   70   61 C.O.R.   .784    .778    .780    .770    .757 Shore C Hardness   88   88   88  88   89 Spin (R.P.M.) 8,825 8,854 8,814 8,990 8,846 Cut Resistance 3-43-4 3-4 3-4 1-2

[0192] As it will be noted in finished balls 1-4, by creating amulti-layer cover utilizing the high acid ionomer resins in the innercover layer and the hard/soft low acid ionomer resin in the outer coverlayer, higher compression and increased spin rates are noted over thesingle layer covers of Table 21. In addition, both the C.O.R. and theShore C hardness are reduced over the respective single layer covers ofTable 21. This was once again particularly true with respect to themulti-layered balls containing the high acid ionomer resin in the innerlayer (i.e. finished balls 1-5). In addition, with the exception ofprior art ball 5 (i.e. the '193 patent), resistance to cutting remainsgood but is slightly decreased. As note above, the prior art ball of the'193 patent suffers substantially in durability (as well as inresiliency) in comparison to the balls of the present invention.

[0193] Furthermore, it is also noted that the use of the high acidionomer resins as the inner cover material produces a substantialincrease in the finished balls overall distance properties. In thisregard, the high acid ionomer resin inner covers of balls 1-3 produce anincrease of approximately 10 points in C.O.R. over the low acid ionomerresin inner covers of balls 4 and about a 25 point increase over theprior art balls 5. Since an increase in 3 to 6 points in C.O.R. resultsin an average increase of about 1 yard in distance, such an improvementis deemed to be significant.

[0194] Several other outer layer formulations were prepared and testedby molding them around the core and inner cover layer combination toform balls each having a diameter of about 1.68 inches. First, B. F.Goodrich Estane® X-4517 polyester polyurethane was molded about the coremolded with inner layer cover formulation A. DuPont Surlyn® 9020 wasmolded about the core which was already molded with inner layer D.Similar properties tests were conducted on these golf balls and theresults are set forth in Table 24 below: TABLE 24 Finish Balls 6 7Ingredients: Inner Cover Layer A D Composition Outer Cover LayerEstane ® 4517 Surlyn ® 9020 Composition Properties of Molded FinishedBalls: Compression    67   61 C.O.R.     .774    .757 Shore C Hardness   74   89 Spin (R.P.M.) 10,061 8,846 Cut Resistance 3-4 1-2

[0195] The ball comprising inner layer formulation D and Surlyn® 9020identifies the ball in the Nesbitt U.S. Pat. No. 4,431,193. As is noted,the example provides for relatively high softness and spin rate thoughit suffers from poor cut resistance and low C.O.R. This ball isunacceptable by today's standards.

[0196] As for the Estane® X-4517 polyester polyurethane, a significantincrease in spin rate over the TE-90 cover is noted along with anincreased compression. However, the C.O.R. and Shore C values arereduced, while the cut resistance remains the same. Furthermore, boththe Estane® X-4517 polyester polyurethane and the Surlyn® 9020 wererelatively difficult to mold in such thin sections.

[0197] In yet another series of experiments, golf ball cores comprisinga silicone material were formed in accordance with the presentinvention. Shinetsu X-832-071-1 silicone material (base and catalyst)was obtained and a silicone molding material was prepared. The materialwas degassed for approximately 7 to 10 minutes. The flowable materialwas then transferred into hemispherical, or nearly so, molding cavities.The molding cavities are Teflon coated. An excess of material wasdeposited into each molding cavity to form a positive meniscus. Themolds, filled with silizone molding material, are placed in an oven forabout 4 to about 6 minutes until the skins form on the siliconematerial. Each of the molded silicone hemispheres are then joined toanother corresponding silicone molded hemisphere. Registration andplacement of the molded halves may be controlled by conventionalclamping assemblies. While compressed together, the molded assembly isreturned to the oven for approximately. 25 minutes. After sufficientcuring, the molded assembly is cooled by immersion or spraying with coolwater. The Shore 00 hardness of the resulting molded core was 98.

[0198] A silicone layer, molded about a core, was formed as follows inaccordance with the present invention. Shinetsa X-832-071-1 siliconemolding material was appropriately prepared and degassed. The flowablematerial was transferred into hemispherical, Teflon coated moldingcavities. Each mold is filled until about one-third full. The partiallyfilled molds are placed in an oven and heated until a skin forms uponthe silicone molding material. The molds are then removed from the oven.A preformed core, either conventional or a silicone core as describedherein, is then appropriately positioned within each mold, centered andpartially contacting the skinned silicone material. The core ispreferably pressed downward into the mold until the silicone materialraises, preferably to the top (or brim) of the hemispherical moldingcavity. Another partially filled mold containing skinned siliconematerial, is then placed over the core and other mold half. Conventionalclamping assemblies may be employed to ensure proper registration of thehalves. The resulting assembly is then placed in an oven forapproximately 25 minutes until the silicone layer is sufficiently cured.The molded product is removed and cooled with water. The Shore 00hardness was 100.

[0199] In yet another series of experiments, golf balls in accordancewith the present invention were prepared as set forth below and in Table25.

[0200] Silicone base and catalyst were thoroughly mixed and thendegassed for 7-10 minutes. Mixed material was poured into 1.40″ diameterhalf shells and these were placed in an oven to skin over. They werethen removed and the two halves were clamped together to form a wholecore and placed back in the oven for final cure. After curing, a mantlelayer was formed over the cores via injection in two sizes, 1.71″ and1.72″. Static data was measured after each stage and is listed below.TABLE 25 Multi-layer Golf Ball With Silicone Rubber Core Example AExample B Core Material Shinetsu X-832-071-1 Shinetsu X-832-071-1 Size 1.400″  1.400″ Weight 25.2 g 25.2 g Shore 00  82  82 100″ Drop Rebound 54″ 54″ Mantle or Interior Layer Materials   50 pph   50 pph Iotek 1002  50 pph   50 pph Iotek 1003  1.57″  1.57″ Size  0.085″  0.085″Thickness 34.5 g 34.5 g Weight *1 *1 Comp 643 643 COR 70-71 70-71 ShoreD Molded Ball Materials   38 pph   38 pph Iotek 1002 52.6 pph 52.6 pphIotek 1003  9.4 pph  9.4 pph TG MB 171″  1.72″ Size  0.070″  0.075″Cover Thickness  43.2  44.1 Weight  90  90 Comp 728 731 COR  70  70Shore D

[0201] The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon reading and understanding the proceeding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

We claim:
 1. A golf ball comprising: a core; a cover layer; and at least one interior layer surrounding said core and disposed between said core and said cover layer; wherein at least one of said core and said at least one interior layer comprises a silicone material selected from the group consisting of silicone polymers, silicone fluids, silicone elastomers, silicone resins, and combinations thereof.
 2. A golf ball according to claim 1 wherein said silicone material is a silicone polymer.
 3. A golf ball according to claim 1 wherein said silicone material is a silicone elastomer.
 4. A golf ball according to claim 1 wherein said silicone material is a silicone resin.
 5. A golf ball according to claim 1 wherein said cover layer comprises an inner cover layer molded on said at least one interior layer, and an outer cover layer molded on said inner cover layer.
 6. A golf ball according to claim 1, wherein the interior layer has a thickness of about 0.100 to about 0.010 inches and the cover layer has a thickness of about 0.010 to about 0.05 inches, the golf ball having an overall diameter of 1.680 inches or more.
 7. A golf ball according to claim 6 wherein the interior layer has a thickness of about 0.0375 inches and the cover layer has a thickness of about 0.0300 inches, the golf ball having an overall diameter of 1.680 inches or more.
 8. A golf ball according to claim 1 wherein said silicone material, upon curing, has a Shore 00 hardness of from about 55 to about
 100. 9. A golf ball according to claim 1 wherein said silicone material, upon curing, has a tensile strength of from about 300 psi to about 600 psi.
 10. A golf ball according to claim 1 wherein said silicone material, upon curing, exhibits an elongation of from about 350% to about 650%.
 11. A golf ball comprising: a core comprising a silicone material; an inner cover layer molded on said core; an outer cover layer molded on said inner cover layer; and at least one interior layer disposed between said core and said outer cover layer, said interior layer comprising a silicone material.
 12. A golf ball according to claim 11, wherein the inner cover layer has a thickness of about 0.375 to about 0.010 inches and the outer cover layer has a thickness of about 0.010 to about 0.375 inches, the golf ball having an overall diameter of 1.680 inches or more.
 13. A golf ball according to claim 12 wherein the inner cover layer has a thickness of about 0.030 to 0.375 inches and the outer cover layer has a thickness of about 0.030 to 0.375 inches, the golf ball having an overall diameter of 1.680 inches or more.
 14. A golf ball according to claim 11 wherein the outer layer composition includes 90 to 10 percent by weight of a hard high modulus ionomer resin and about 10 to 90 percent by. weight of a soft low modulus ionomer resin.
 15. A golf ball according to claim 14 wherein the outer layer composition includes 75 to 25 percent by weight of the hard high modulus ionomer resin and about 25 to 75 percent by weight of the soft low modulus ionomer resin.
 16. A golf ball according to claim 11 wherein said silicone material, upon curing, has a Shore 00 hardness of from about 55 to about
 100. 17. A golf ball according to claim 11 wherein said silicone material, upon curing, has a tensile strength of from about 300 psi to about 600 psi.
 18. A golf ball according to claim 11 wherein silicone material, upon curing, exhibits an elongation of from about 350% to about 650%. molding a layer about said core component at conditions suitable to adhere said layer to said core component.
 20. The method of claim 19 wherein said layer is a cover layer.
 21. The method of claim 19 wherein said layer is an intermediate layer disposed between said core component and a cover layer.
 22. A method of producing a golf ball including a silicone material, said method comprising: providing a core component; disposing said core component in a mold adapted for forming at least one of a golf ball and a golf ball component; molding a silicone material about said core component to form an intermediate layer on said core component; and forming a cover layer on said intermediate layer to thereby form said golf ball.
 23. A method of producing a golf ball, said method comprising: preparing a silicone material suitable for use in golf ball by combining at least one silicone elastomer and silicone elastomer precursor with an effective amount of a reinforcing material; forming a golf ball core comprising said silicone material; and molding a layer about said golf ball core.
 24. The method of claim 23 wherein said layer is an outer cover layer.
 25. The method of claim 23 wherein said layer is an intermediate layer disposed between said golf ball core and a cover layer.
 26. The method of claim 23 wherein said reinforcing material is selected from the group consisting of silica, alumina, zirconia, calcium carbonate, clay, silicates, aluminates, fibrous fillers, zinc oxide, iron oxide, titanium dioxide and combinations thereof.
 27. The method of claim 26 wherein said reinforcing material is silica.
 28. The method of claim 27 wherein said silica has a specific surface area of from about 20 to about 400 m²/g.
 29. A method of producing a golf ball comprising: providing a golf ball core component; placing said golf ball core component in a mold; preparing a silicone material by combining at least one silicone elastomer and silicone elastomer precursor with an effective amount of a reinforcing material; and molding said silicone material about said golf ball core component.
 30. The method of claim 29 further comprising: molding a cover layer on said silicone material.
 31. The method of claim 29 wherein said reinforcing material is selected from the group consisting of silica, alumina, zirconia, calcium carbonate, clay, silicates, aluminates, fibrous fillers, zinc oxide, iron oxide, titanium dioxide and combinations thereof.
 32. The method of claim 31 wherein said reinforcing material is silica.
 33. The method of claim 32 wherein said silica has a specific surface area of from about 20 to about 400 m²/g.
 34. A method of preparing a golf ball comprising: providing a golf ball core; positioning said golf ball core in a mold; providing at least one room temperature vulcanizing (RTV) silicone elastomer; forming a layer about said golf ball core by encapsulating said golf ball core with said silicone elastomer.
 35. The method of claim 34 wherein said room temperature vulcanizing (RTV) silicone elastomer is a one-component RTV silicone rubber.
 36. The method of claim 34 wherein said room temperature vulcanizing (RTV) silicone elastomer is a two-component RTV silicone rubber.
 37. The method of claim 36 further comprising: curing the layer formed about said golf ball core by heating to a temperature of from about 50° C. to about 150° C.
 38. The method of claim 34 further comprising: curing the layer formed about said golf ball core by exposing said layer to gamma or high energy electron radiation.
 39. The method of claim 34 wherein said layer is formed by molding at a temperature of from about 100° C. to about 180° C., and a pressure of from about 800 psi to about 1500 psi.
 40. A method of producing a golf ball, said method comprising: preparing a silicone material for use in said golf ball by combining a silicone resin with a suitable catalyst; forming a golf ball core that includes said silicone material; and molding a layer about said golf ball core.
 41. The method of claim 40 further comprising: molding a cover layer on said layer molded about said golf ball core.
 42. A method of producing a golf ball, said method comprising: providing a golf ball core; placing said golf ball core in a mold; preparing a silicone material for use in said golf ball by combining a silicone elastomer with a suitable catalyst; and forming a layer of said silicone material about said golf ball core.
 43. The method of claim 42 further comprising: molding a cover layer on said layer of silicone material. 